Sure they believed it, but that doesn't mean they were violent or dangerous. There weren't going to be any politicians dangling from lightposts that day. Left alone for long enough, they would've eventually got bored and gone home.

Far worse things were said of Trump every day on Twitter throughout his presidency (and beyond), I don't think empty threats from the frustrated and powerless are anything to be taken seriously.

All of this hasn't stopped the US Gestapo locking up political opponents for decades as a result of Jan 6th, even those who didn't even attend. So it was a very useful day for one side. It makes even more sense when you consider that they refuse to release video evidence from the day because of how many feds' covers they'd blow.