The Thalmor were racist dicks that had some very messed up views on reality and how they should be able to blow it up. They believed that the time before existence, they were on the level of gods because they were unfettered to any concept of ‘real’. Then some of the gods decided to create reality and anchor themselves to it and created mortal races, which caused reality to ensue, and suddenly things could grow old or get stabbed and.

Basically they didn’t like the concept that they aren’t perfect and wanted to go back to a state where they didn’t have to deal with lesser beings or deal with the consequences of...you know. Life.

Even it was true, it’s a very self-destructive mindset, as you might have noticed. If you are above everything and you’ll be going back to being an invincible not-thing, what do you care about the suffering you cause to get there, right?

And yeah, that is exactly what she tried to do.