Yeah I really don't understand the over-the-top infatuation with her in particular. She's not that great of an actress from what I can tell. She has a very flat affect (the "dead eyes" you mention) which can be a good thing and just what certain roles call for but not great for versatility and expressivness in general. And there are countless other conventionally beautiful actresses that can check off all the same tickboxes for mass/pop-culture appeal that Sweeny can. I guess it all has to do with being in the right place at the right time and doing a bit of work in some crass and culture-war adjacent things, like that dog-whistley jeans commercial, that made the chuds latch onto her symbolically as the quintessential Murican woman.

I think that's the reason why the chuds love her, it's basically their fantasy