Got it. Moral of the story, Ferelden should never rebel against Orlais and take their land back. And Andraste shouldn't lead an army to fight Tevinter as they have no hope of winning. 
Fereldan was a matter of chance and politics things came together and it became worth more to abandon the territory then to hold it.
And Tveinter crumbled after it endured a blight, remember that; Had that not occurred? Well i doubt the Imperium would have fallen considering it maintained the largest military well...in history.
Neither of these things really apply to the Orlaisian proper mind you.
Orlais has been defeated, lost wars, but it has always remained in its position of superiority remember that.
Why is that? How has it lost and not yet crumbled like the Imperium? Why is the wealthiest Nation in Thedas? Why does it maintain the greatest military? All these questions revolve around what exactly makes Orlais, Orlais and you know what is? The Ability to Unite, To put aside petty differences when it comes to matters of war and state. The game continues mind you, but why be King of a field of ashes? They realize that.
Its why the game never endangers Orlais it self, If it ever does...Well you see what occurs in history, Leliana got a small measure of that.