I can't get off my head that it was all a Tevinter plot put in motion right from the moment when mages were being locked up in the Gallows. Or even before that.
Anders went to Kirkwall solely to save Karl (Marx, hehe) and ends up getting involved with a subversive group (which mage Hawke never gets to join, though he's also an apostate (???)) called The Mage Underground. It sounds like a rock band, but it's pretty serious.
There's no way these mages did not know Anders had a spirit within him. And for some personal reason, Anders wanted to get back at the templars long before he received news of Karl. Add Karl's death to that, his lover's death, and you have a possessed mage who's deeply upset and ready to do anything it takes to avenge him. So what do the mages do?
Convince him to deliver a deadly blow to the templar order: to destroy the Chantry.
But here's the catch: he doesn't kill templars. He doesn't kill Meredith. Instead, he destroys something entirely different. Anders destroys the only thing that ensures control over both mages and templars.
If he were thinking rationally, he'd be like: Wait, why am I blowing the Chantry and not launching a suicidal attack against the templars themselves?
Now let's think about the Mage Underground and the rogue mages in Kirkwall.
Who formed the group?
We don't know.
Who funds it?
We don't know.
Who commands it?
We don't know.
How do they get secret information?
We don't know.
Who issues the orders to the mages?
We don't know.
What we DO know is that Anders obtains a lot of information from this organization.
Notice how he progressively becomes involved with the group throughout the 3 Acts. After he loses Karl, Anders focuses solely on revenge. From then on, all goes downhill.
Now let's think about the overall situation in Kirkwall, a few events and just how bizarre all of it really is.
What is the biggest threat to the city?
Blood mages infiltrating it and converting other mages (some even from the Circle) to use blood magic.
Also, slave traders who infest the city, ready to ship their victims to Tevinter.
What does Fenris say to us in order to alert us from the very moment we step on the Gallows (which is by coincidence the last place we visit and where the final battle takes place)?
That mages cannot be allowed to be their own watchers. Otherwise, this leads to a different type of tyranny: a magocracy.
What do we give Anders as a token of appreciation?
A Tevinter amulet, symbolic of a society where, in his head, mages are free. But Fenris alerts him that that notion is false! There's also oppression there, of the most powerful mages, the Magisters, over the weaker ones.
Meredith confessed the attacks on Kirkwall from rogue mages were increasing. We never really learn why, but it makes no sense that the mages simply decided to rebel by themselves without having external help. Mages are kept locked in a Tower ever since they are very young. They know literally NOTHING about the world out there.
And then, suddenly, dozens of them are fleeing, hiding into caves they couldn't have found without help.
And what about the absurd amount of blood mages just entering the city? Where do they come from? Blood magic is forbiden in the Free Marches. And mages are recruited from an early age to join the Circle. Notice how there's a constant effort to disrupt the Circle in Kirkwall, which is one of the most important cities in the Free Marches.
This cannot be just a coincidence.
Back to the terrorist attack, I have serious doubts that this was Anders's idea.
First, because Anders never kills anyone willingly. He only tries to save his friends. If he's threatened, then he'll attack.
Secondly, because he works hard on his Manifesto. He's a dreamer, a philosopher, a politician. Not a terrorist or a killer. He prefers to convince by the strength of his beliefs than by forcing you to bend to his will.
Therefore, whoever gave the idea to blow the Chantry knew Anders was ready to be a martyr.
That same person -or people- also knew that, with the Chantry destroyed, the already tense situation in Kirkwall would escalate to civil war. The only thing keeping the (fragile) peace between mages and templars would be gone.
And there's also this: the only branch of the Divine in Kirkwall is the Chantry.
Remember how Leliana tells us that the Divine was investigating the actions of separatist mages' groups in the city? The Divine knew there was something more in this sordid affair. Something that, after Anders's terrorist act, never came to surface.
This was not a simple act of martyrdom. This had nothing to do with setting mages free. The target was the Divine all along.
Now let's make it all come together: What nation in Thedas is known to be ruled by blood mages, to be considered a safe haven for apostates, has powerful magic at its disposal -the sort that can, shall we say, BLOW UP A WHOLE BUILDING- and rejects the Divine?
Whoever planned this wants to destroy the Chantry, which is the only institution capable of stopping the influence of the Magisters of Tevinter from expanding its empire to the Free Marches and submitting the entire land to a magocracy.
Remember how the Guardian of Andraste's Ashes tells us that the Tevinter Imperium is soon coming to an end?
This is an act of desperation from the Magisters, an attempt to expand their dominion and prevent the inevitable end.
With the Divine gone, now the Magisters have free access to the Free Marches, acting through their agents spread in every country. Destroy the Divine and you destroy the very institution that symbolizes Andraste's resistence against Tevinter, against the followers of the Old Gods.
And what do we hear about in Inquisition? That the Elder One, summoned by a Magister, wants you to bow to him...an Old God, perhaps?
It is my belief that, in the end, Anders was used. He was naive. He thought he was fighting to free the mages. But he only paved the way for the tyranny of Andraste to be replaced by another one: the tyranny of an empire of mage slavers.
The true terrorists were the Magisters, who plotted against the Divine and set in motion a diabolical plan through their many agents, influencing the minds of a few desperate mages, like the ones in the Mage Underground. All they needed was a martyr. And then, they found Anders.
And with a spirit like Justice in your head, goading you to follow the road to Hell itself in the name of righteousness, no one could have chosen to walk away from this. Anders was doomed from the start. It's a pity that not even Hawke's love could save him from this.
But of course, the whole Tevinter theory could be just utter crap. Maybe it was just a bunch of separatists behind the attack all along. I'll just have to wait until November to see if any of this adds up.
Sorry for the long post. Please don't cut my head off. Not without numbing my mind first, anyway...