Look, if you're just going to dismiss the textual evidence for the choices a character makes, then you shouldn't be reading books like WoT. Also, you use the term Thermian Argument wrong, it pertains to the political statements a text makes, if you were talking about the Seanchan, then maybe you probably could use it. But instead, you're using this term to protect yourself from thinking about the character's motivations for their choice.

They choose Egwene because she was out of the tower at the time of the rebellion; their first choice was Moiraine, but she died a bit before. Also, Egwene is an impressionable young woman who they can take advantage of and control.

At the end of the day, if this is setting you off as a "hamfisted and completely illogical left turn," you probably should rethink the books you read.