> why people who are already breaking one law would care about the others

Remind me not to get in your way when you're jaywalking.

Premeditating a felony firearms offense is one thing. I think the majority who entered the Capitol were probably thinking that most of the rhetoric they were hearing beforehand was hyperbole and were probably expecting to just protest outside the capital, and then got swept up in the moment and committed misdemeanor/felony breaking-and-entering.

Protests are big drinking events. For some reason people don't talk about this. Angry people go out planning to peacefully protest for George Floyd or Trump, they drink some liquor, their inhibitions go down, they decide to throw a couple bottles, break a couple windows. It's hard to miss the number of red faces in the videos of the capital riot.