Late Stage Capitalism

It’s because Republican voters are conditioned to vote ( R ) no matter what, whereas Democratic voters will actually use their brains and vote for opposition

I don't think there's actual evidence to back up this supposed conventional wisdom. It seems to me that Republican voters are a lot more likely to draw lines in the sand over things like abortion or guns, and to denounce anyone who doesn't take a hard line on their stance as a "RINO." The Libertarian party has often gotten more votes than the Greens, and the last major third party candidacy was Ross Perot who drew mostly from the right. I rarely see any of the same kind of vote-shaming, lesser-evilist discourse on the right. In right-wing circles, if someone says they firmly believe abortion is murder so they refuse to vote for a center-right candidate who's pro-choice, that's a lot more likely to be respected. The right doesn't have the same commitment towards "reasonableness" that liberals do and don't shy away from "my way or the highway" rhetoric.

It seems to me that what's actually different is that the Republican party has acknowledged and responded to the demands of their base. The right has no reason to abstain because their politicians are giving them exactly what they asked for, while the Democrats have followed the logic that elections are won by appealing to the center, and that the left will simply fall in line regardless. That logic is another piece of "conventional wisdom" that isn't actually supported by the evidence.