They think Trump will suspend all elections and ban Democrats from existing. Or they think he'll erase the conditions necessary to be a liberal. Or he'll embarrass liberals in front of their fancy European peers. American liberals conceive of themselves as perpetual underdogs, only ever just achieving victory. They conceive conservatives as the natural state of the universe. They consider conservatives not as a historical feature or representing certain economic classes, they see conservatives as representing baseline humanity. It's what humanity is without culturally instructed liberalism, basically. They're logic and reason people who believe they're overcoming "human nature" through dissemination of cultural liberalism.

So they think people like Trump are the antithesis of this project and they'll make liberalism extinct, forever. I'm pretty sure this is why they conceive of us as the same thing as conservatives, or why they throw around the word authoritarian. Because we're also opposed to liberals operating governance.