So, we all know the theory that Thalmor “wants to destroy the world by using/destroying the Towers”-theory, right? Well, it’s just a fan theory that got popular and isn’t really based on anything, so I don’t particularly like it (but if it reaches enough consensus in fandom it might end up being turned into canon by Bethesda. Canon in Elder Scrolls is kind of influenced that way).
So with that out of the way, I will present to you my current favorite Thalmor Theory:
The Thalmor were founded by Ayleids.
And not just any Ayleids, but the Alessian Ayleids who aided in the slave rebellion against their kin, only for the humans to turn against them and forcing them to either die or run away and hide in provinces other than Cyrodiil.
Now, understandably, these Ayleids weren’t happy with being run out of their homes for daring to help humans by humans. The ones who survived to other lands were also powerful, probably mages, and as such very long-lived (and thus probably one or two or maybe even three survive well into the 4th Era and the Dragons’ return).
A large number ends up in Summerset. Where they lick their wounds and work on getting over their traumas and whatnot to salvage what life they can. They might marry Altmer and have children and families and friends and things look up.
And then Tiber Septim rolls in and commits genocide against the Altmer until the Altmer king/queen bends the knee to the Empire. And then the Empire forces the Altmer to worship Tiber Septim as the god Talos.
The Ayleids and their descendants, having lost family and friends on a massive scale once more to the Empire, has had enough. They found the Thalmor, but because it is a very Ayleidic in its undercurrents, they have trouble attracting pure Altmer, and in combination with bending the knee to their oppressors, the Ayleids starts to dislike the Altmer as well. They start to pick part-Ayleids as future spouses to preserve the Ayleid way/genes instead, which is what they really mean with “purebred” (most Altmer does not know this and think they’re breeding pure Altmer with their arranged marriages).
Ayleids, unlike Altmer, were also known to worship daedra, which was how they knew how to make it look like they saved the world from the Oblivion Crisis, on top of that, they have Ayleidic cousins among the Boiche to help them incorporate Valenwood into their new Dominion.
And, of course, Lord Naarifin had a dremora right hand wielding the artifact of Boethiah, while using the Orb of Vaermina, and then being carried away by winged daedra (winged twilights?) from his imprisonment after he lost the Imperial City.
It should also be noted that in Legends (after Oblivion), the Imperial City is shown with the Temple of the One and not the petrified Avatar of Akatosh.
I believe that Naarifin (an Ayleid, or part-Ayleid, Thalmor leader) had the Avatar of Akatosh removed, pending destruction, (if it maintains, or in any way supports, the liminal barrier against Oblivion, it would be in both Boethiah’s and Vaermina’s, and, indeed, all daedra’s, interest to destroy it. Or it might be the key to reopen the barrier), and the Temple of the One rebuilt. Because the Avatar is the symbol that Martin Septim, not the Thalmor, had ended the Oblivion Crisis (and the Temple of the One would have been mentioned many times in literature, and changing it to giant dragon statue in millions of books is harder than getting rid of said statue and rebuilding the Temple), and would have cost them most of their Summerset support.
And it could have been payment to the daedra the Thalmor are allied with for their artifacts and underlings, alongside the Culling (which, without the Avatar, might have reopened the barrier by number of souls alone, many of them daedra worshipers in this City of a Thousand Cults, going to the Planes of Oblivion).
But basically, what the Ayleidic Thalmor wants is not to destroy the world. What the Thalmor wants is to destroy the Empire, and possibly, Men, for what they’ve done to them. Outlawing Talos worship might have started the rebellion with the Nords, but was just as much motivated by their sheer loathing of him and his empire.
