Who are the marginal traders who determine prices though? Long-term holders don't trade. By the time they assert their view it's too late.

Much more complicated than that though market price action dynamics do play a role in corrupt corporate governance at some remove.

Different market participants will be trading on different signals, sentiments, or theses, and this will influence everything from the order types they use to the hold time of the instruments in question.

But one of many things they all have in common is that they know that what other people think about the future affects the price right now: an intuitive proof of this is that if some major announcement is made about e.g. trade policy, and the market deems it credible, you will see instruments transact up or down in price immediately.

In any effort to go deeper, one must be wary that this goes from market microstructure to Ito calculus to voodoo real fast, a closed form solution would be an infinite money machine! But a reasonable jumping off point might be the notion of a Keynsian Beauty contest: https://en.wikipedia.org/wiki/Keynesian_beauty_contest

The TLDR is that hold times across like 13 orders of magnitude (rumor has it a cutting edge FPGA fielded by someone like Optiver or HRT or Virtu can pull a whole ladder in 20-50ns glass-to-glass, so whatever Buffet does divided by that) the market still in some sense reflects expectations about the future: it's "priced in" in trading parlance.

"Too late" has some ways you can use it meaningfully in finance, but it's not in the sense I take you to mean above.