Future cash flows is usually pretty strongly related to the current state of things, but adjusted based on expectations of how it will play out in the future.

I'd be surprised if a non-negligible fraction of investors actually made that calculation. Most buy for other reasons.

Then we have the ginormous index funds who buy when buys are happening.

We just collectively decided that the best thing for society is if everyone just buys stocks for their savings. Either directly or through pension funds. And now we're pretty much stuck with that.