You pandaren tried to bury your hate and your anger, but such power cannot be contained. It must be unleashed!
- Garrosh Hellscream to Taran Zhu
The more I think about it, the more I believe it. This was all going to happen, with or without the presence of the Horde or Alliance. In fact, the presence of those two warring forces may have ultimately saved Pandaria from complete destruction. When Garrosh Hellscream defeated Taran Zhu and hurled the Heart of Y'Shaarj into the waters of the vale, he mocked the Shado-Pan's leader first about the pandaren and their tendency to suppress violent emotion. It's an understandable tendency in a land where emotions like doubt, anger, fear, and hatred can give rise to the Sha, but it was a tendency mired in one crucial error - there was always one Sha who wasn't imprisoned when Emperor Shaohao freed himself of the burdens of the others. For over ten thousand years, Pandaria dwelled in isolation, believing itself special among all the places in the world, believing that it had nothing to gain and nothing to learn from the outside. And in its special exceptionalism, its beautiful but stagnant isolation, the people of Pandaria settled into an eternal and endless cycle that allowed nothing to change it.
But a thing that does not change is not alive.
It's painful to look upon the Vale of Eternal Blossoms after Garrosh's actions, to see the blasted, corrupted land where waters flowed freely, to see the destroyed and defiled beauty. Taran Zhu blamed all those who came from outside Pandaria, and he's not wrong - it is because, at long last the mists have parted and new peoples have entered Pandaria that the Vale was destroyed, just as it was because of the same outsiders and their foreign war that the Sha of Doubt erupted and the serpent pillar fell. Destruction had indeed followed in our wake.
This lesson is supremely hard to learn, and harder still to accept it - indeed, even as he's being led from the chamber where Y'Shaarj's heart slumbered for eons, even as he is rescued from the Sha of Pride itself, Taran Zhu has yet to learn it. The pandaren people suppress negative emotions like their fear and their hate, but they do not suppress their pride - they are a very proud people. They believe they have good reason to be - they overthrew their mogu tormentors despite all the odds being stacked against them, they too defeated the Zandalari who sought to aid the mogu, they stand fast and hold back the mantid and the yaungol and do all this without falling prey to the base passions of other races. They are the inheritors of Shaohao, a people who need nothing from the outside world - when the foolish night elves brought devastation down upon the world it was the pandaren who were wise enough to see it coming and fortunate enough to be protected by their Emperor.
The realm you see all around you was mine to command.
I conquered my doubts, my fears, my anger... I buried all of it within the land.
But I held on to one vice. The one sha I never conquered. PRIDE.
My pride cloaked this land in mists! I thought we were better than the rest of the world.
I thought we could solve our own problems. But for ten thousand years, we stagnated, our doubts and fears buried in the land, rising up to fester whenever we allowed them.
Pride. It is the most insidious of sha. It is good until it is bad. And then it is more dangerous than all the others combined.
Beware of Pride! Be humble! The world is plunging into chaos. Old enemies must work together. Proud races must admit they need help.
Things are going to get worse before they get better. Only by working together can we overcome the darkness.
All that stands in our way... is pride.
- Emperor Shaohao, Path of the Last Emperor
And so their pride cloaked them from the world for thousands of years. So proud were they of their way of life, they never saw any way to change it, any reason to change it - and so it stagnated. Generations of young pandaren would join the Shado-Pan, and there be taught to control themselves and their base emotions - honed to an edge of martial skill and discipline that would allow them to face actual horrid manifestations of violence, fear and anger, emotions given substance and form. And they would defeat them, for the good of Pandaria as a whole. They were the bastion of their people, defenders against all threats. And they knew that they were the best of the best - and they grew proud.
We can see this now in Taran Zhu's manner from the first moment he meets the Alliance and Horde forces - he displays no curiosity, no desire to understand who these strangers from beyond the mists are, he only displays disdain and a haughty demand that they cease their actions immediately. Does he know the Sha better than they do? Absolutely he does. But does he bother to even attempt to explain? No. He knows he knows better - he is pandaren, the leader of the Shado-Pan. It is not his knowledge that is ever in question, but rather his own ability to do that which he demands of others. Taran-Zhu proves twice that he is not beyond the control of the Sha - first, by falling prey to the Sha of Hatred within his own monastery (and further, by then allowing himself to obsessively hunt for said Sha in the Townlong Steppes) but moreover, throughout his interaction with the outsiders - whether it be in the White Tiger Temple, or on the Isle of Thunder - Taran Zhu shows himself to be proud, and disdainful of those he has to deal with.
The worst part of all this is, it's not even his fault. The Shado-Pan were created by Emperor Shaohao during his reign - their origin as an order is rooted in his actions and his great, fundamental mistake, his failure to root out Pride. They alone of all pandaren are allowed to tap into their negative emotions, their anger and violence, using the Sha's own methods against them - had they known of Pride's continuing presence they could have presumably tried to do the same against it, but they were unaware. Even as the racial pride of the pandaren served to create a vast reservoir of power the Sha could feed on endlessly, their was no way for those within its grasp to realize what was happening, and the results seemed wholly beneficial to them. "Pride is good, until it is bad."
I am not saying Garrosh Hellscream was right to do what he did. But he was right, in part, in what he said - the pandaren tried for over ten thousand years to create a society where hate and violence were buried, suppressed. They did this because they believed that to allow those emotions free reign would be to allow powerful destructive forces to ravage their land, and they were correct - but there's a difference between burying one's feelings and controlling them. By allowing themselves to be slaves of pride, the pandaren created a place where the other Sha would always rise again, where the Shado-Pan were locked in an endless battle against emotions themselves. These emotions cannot be destroyed, and they cannot be suppressed - in the long run, they must be faced, and they must be channeled and controlled. Doubt would have led the pandaren to question why they were so convinced of their own superiority. Fear might have led them to change their ways. Hatred could have motivated them to do something, anything, instead of accepting stasis for tens of millennia. Violence can be controlled and harnessed, and even despair and anger have their places, they can be used positively as long as they don't control you.
Ten thousand years ago, Emperor Shaohao made a decision to shelter and protect Pandaria against the Sundering, a decision made out of love for his people and his land, yes... but moreover, one made out of his pride, his hubris. He chose his people to be spared what the rest of the world would endure - he removed his people from the world, from the ills of the Sundering, yes, and from every possible good or ill outcome to follow. He lacked the humility to accept that his people, his land were part of the world, and the Sha of Pride made use of that hubris to create a place where it could dwell forever, and feed forever. This mistake had consequences for his people till the moment the mists parted, when outside feet once again walked the shores of Pandaria. The peoples of the sheltered continent were forever trapped within a prison of Shaohao's making, bound by his pride.
The damage we see to the vale is horrific. It is a reminder and a warning that Pandaria cannot ignore the outside world any longer. The dead like Rook Stonetoe and Sun Tenderheart didn't deserve their deaths, and we can't pretend that what happened was a good thing. But a forest fire isn't a good thing to the animals it kills, and yet, it brings new life to the forest it burns. Stagnation can be painful, agonizing, traumatic to leave behind, and yet it still must be left behind. The longer you fight change - the longer you hold back the avalanche - the worse the day when it comes. And as sad as the destruction of the vale and the deaths of those who fell to Hellscream's actions, this day was inevitable. Pride had to fall, not just for Pandaria, but for the entire world. The prison had to be broken.
This was all necessary. A thing that does not change is not alive.
While you don't need to have played the previous Warcraft games to enjoy World of Warcraft, a little history goes a long way toward making the game a lot more fun. Dig into even more of the lore and history behind the World of Warcraft in WoW Insider's Guide to Warcraft Lore.