Add Less Lead Exposure. Empathy is a function of the brain and lead damages it.

I think it's your third point, mostly. Maybe even as sharply stated as: boomers became more conservative as the system and status quo brought them wealth, comfort, and security, so naturally they wanted to keep that going. For the generations that have followed, the system and status quo have only continued to bring those benefits to the boomers, not to them, so they're less likely to trend conservative to perpetuate a system that has failed them.

Additionally, in the years since the boomers came of age, the political right has moved away from a traditional conservative platform to a very extreme and hateful version of itself. Even if many millennials had shifted slightly to the right as they aged, the party typically associated with conservatism has moved so much farther to the right that even with their gradual shift, these millennials are still far closer to the left, or at least to "not whatever the right is saying".

More people become conservative when they have something to lose. Why would you want to conserve a status quo where you don't own anything of substance and probably never will?

while the last point is perhaps the main determinant theory behind why many older people are not being owing more right wing, I'm a little confused by your first two points.

especially the fact that people have greater access to knowledge and are forced to think more critically. if anything, with the advent of the internet, echo chambers have never been easier, preventing critical thinking. this leads to a growing of extreme positions which further reinforces such views due to tribalistic fallacies in our thinking and the need for these tribal identities to distinguish themselves.

I also think having kids has an impact, which we're not doing as much.

That's very true. could you explain your statement about "picks off the weak"?