What is it about FSD that results in this valuation though?

If elon builds a time machine and goes to the future to get FSD tech from 100 years from now and rolls it out to all teslas tomorrow, what will change? Will every car driver get rid of their cars and get a tesla? Will that suddenly justify the stupid valuation?

Realistically, I don't think the majority of drivers will care that much. Sure, their sales will go up, but I can't see it going up by that much.

FSD will never be "achieved" suddenly. The tech will incrementally improve every year, across all manufacturers until one day we are manual driving only 1% of the time with FSD doing the rest. Like AGI, there is no moat in FSD. This is the natural outcome of the trajectory that we are on right now, and nothing about tesla is making me believe they will offer anything that other OEMs can't.

No, I think the market is much more cynical than that. Tesla is a meme stock similar to bitcoin or GME. Investors are degenerate gamblers, hoping that it will continue to rise because that's what it does atm, and hoping they won't be the one left behind holding the bag when it crashes one day. It's little more than a voluntary ponzi scheme that most big investors openly buy into knowing full well what's at stake.