You make a good point about the primaries. In the previous elections, Bernie Sanders getting shafted definitely shifted a lot of their supporters away from the Democrap Party and Bernie’s social democracy towards socialism (like, working class seizing means of production). It had a real radicalising effect on people. They were being disenfranchised by federal politics so they looked towards unions and direct democratic organising away from the broken electoral system.

Whoever is making the controlling decisions behind the party facade

Money talks - you can’t dominate a US election without it. And most people don’t have the kind of money that talks, so both parties inevitably end up representing the owner class rather than popular opinion of their supporters. Democrat donors don’t want radical changes which would threaten their wealth, so no matter how popular a Bernie is, they’re going to do all they can to block them. On the other hand, while Trump is similarly unorthodox and controversial like Bernie, they’re not really a threat to the owner class’s wealth (Trump himself is a business owner!). So even while many Republican donors did object and push hard for alternatives, they didn’t do a Democrat and obstruct him.