Dems held no primary, Biden strong armed his way into the de-facto nomination for a second term, and was replaced by his VP when he imploded on the campaign trail.
Wrong., Dems held their primaries as usual, and Biden won them as the incumbent (almost) always does. https://en.wikipedia.org/wiki/Results_of_the_2024_Democratic_Party_presidential_primaries
Of course he shouldn’t have run again, but he did. Maybe some other Dems should have challenged him in the primaries, but they didn’t, and they would have failed anyway. By the time he dropped out there was no time to hold another primary and still get a campaign going for a new nominee. So pretty much all they could do was rally around the VP as the successor.
Because they (Trump and propagandists both foreign and domestic) used the migrants and immigrants as scapegoats, which is the same as we will be seeing as more and more European countries also fall to fascism. It’s human nature that their followers blame the scapegoats as the cause of all their problems, and adore the wealthy as their betters who should be in charge.