One note: I don't think this is right. Trump did very-swiftly take over the party, but not because of Obama and Biden. Republicans and Republican-friendly rich dudes and organizations deliberately built up a propaganda machine after Nixon, and that machine molded an electorate very far right with the aim of ensuring they'd always vote against Democrats—but to support a party that shared very little of their cultivated electorate's far-right aims.
I have also spent a lot of time in red areas and come from a mostly-red family, and typical Republican politicians from Reagan on traditionally have talked a pretty unconvincing game and really just run a pro-(big, monopolist)business/pro-rich party when in office. They could depend on their captive electorate because they'd convinced them the democrats wanted to give illegal immigrants jobs grabbing Republican voters' guns while funding their free abortions with taxpayer dollars and handing the US government over to the UN or something (this is, for readers not familiar with this crowd, a glib presentation but not really an exaggeration of the kind of thing these folks really do worry will happen when Democrats get in office, and probably the least-accurate part of that passage is that Republicans might think Democrats would give illegal immigrants jobs rather than just tons of free money to illegally-vote for Democrats or something like that—that this stuff hasn't happened when Democrats have gotten in office doesn't seem to register as meaningful to them, for some reason)
Trump started talking like a Republican voter, not a Republican politician. "Why don't they just build a wall?" "What does NATO do for us?" "Why don't we just ship illegals out wherever we find them, the constitution doesn't apply to them, probable cause doesn't apply, et c." (dip a toe in social media outside left-wing bubbles and you'll see a truly alarming amount of stuff like that latter sentiment) and disturbing support for military action in "lawless democrat cities", "democratic politicians are all constantly doing crimes up to and including secret murders, we should prosecute all of them"—this is shit their media has been telling them is true and good for decades, Trump's just the first option they've had who's crazy enough to act on any of it. You could hear it on AM radio in the '90s, you could overhear it in a rural diner in the '00s, no problem. This is who their voters are, and have been since before Obama, before Biden, and even before Trump.
He took the party over by exploiting a weakness the party itself had spent enormous resources and decades developing in cynically seeking a powerful tool against the Democrats. Their plan worked really well, but left them vulnerable to the first person positioned to credibly claim to want to do all the stuff Republican voters have been told they should want, but denied by their Republican politicians (because a whole bunch of the ideas are wasteful, insane, totally pointless, or extremely dangerous to democracy or the rule of law, so, to economic stability)
For people who have lived decades in red America before Trump, when he started talking, I think a lot of us saw he was dangerous pretty fast. Not because he was saying crazy shit we'd never heard before, but because he was saying crazy shit we'd heard all the time.