Millenials aren't becoming based crusaders.
Heh.
The 60's liberal flower child who became a banker/stockbroker by the 80's was a cliche when Gen X were children. The exact same thing has happened in every generation going back as far as records have been kept.
Whilst "nuance" has become a poisoned term nowadays, the generations have more or less been split politically in half since forever. What does feel different nowadays and might be more seen in millennials over Gen-X and the Boomers is the absolute refusal to budge from political positions. They become almost sacrosanct, probably because politics = morals in lieu of religion = morals. Because politics was far less tethered to morality, that might've factored into why people might've more easily changed party. It wasn't as integral to being at one point.
Nowadays you wouldn't get something like Reagan vs Mondale, or FDR vs Landon, not today with the way politics has changed. Maybe Bush vs Kerry? But no complete 180s. Trump vs Harris
should've been a washout on the scale of something like those (last minute candidate change, cost of living, etcetera) yet it didn't manifest. The people voting dem and the people voting republican see voting for their associated party as a moral duty, akin to lent.
I think another big part of it is people have put their politics online. Opinions become less personal and more public, which injects a heap of ego into it.
Everybody is made aware that you're no longer the same politically as you were 4 years ago, and the views you so adamantly and passionately defended at one point have now changed. You'll invite mockery and derision, and as we've seen before, people might even take action against you for doing so (doxing, harassment, etcetera).
That's been a big thing that's become criticised as well: changing opinions. You
have to be the same as you always was or else you're accused of being a liar, a hypocrite, unprincipled, etcetera. This leads to people - especially younger ones more inclined to post their views online at no-one's behest - being cemented in their politics because it's become intertwined with how they've presented themselves as a person that they can't change it.