One reason is the Democratic Left keep blowing the opportunities Trump presents them with their "holier than thou" attitude - I think the reason Biden won the nomination was that the majority of Democrats simply don't like the Left, and jumped on the first viable alternative. The rush to impeachment is a perfect example of shooting themselves in the foot, instead of staying calm all you get on their propaganda network (MSNBC) is moral outrage. Compare to how Biden handles it, outrage tempered by common sense and restraint, the kind of balance most Americans want.
I think once Biden gets into office, and become the automatic spokesperson for the Democratic party, this perception will shift - he's the "Gerald Ford" of our time, the calming influence that will temper passions, fortunately, Joe should be the beneficiary of an economic bounceback that may lead to a Democratic landslide in 2022, bringing in a bunch of moderates from "flyover states" that will change the balance within the party, moving attention and power from NY, California and Mass, and making it more representative of America as a whole.
Do I think Trump meant for the crowd to attack Congress? No, I don't think Trump thinks. He just loves being in the limelight, and he wanted thousands outside the capital, on camera, chanting "stop the steal." I mean imagine if they had actually gotten hold of Pence and lynched him? Trump simply doesn't understand how crazy some of these people are, as long as they support him and his ego, he's blind to the danger. Look who egged on the crowd, three of the dumbest people around, Trump, Trump Jr and Rudy. It's like "Russian Collusion," only a crazed left winger could have believed that Putin would actively conspire with the Trump people, the gang that shoots each other. The Russians merely took advantage of the situation, while maintaining implausible deniability. In the same way, Trump et al saw the crowd as their media megaphone, oblivious to the agenda of many of the organizers, which went well past Trump (to them, he was their tool to change America).