I don’t think that’s how it would work out since his conflict was very public knowledge before this point. He plausibly disclosed this to the board at some point before Poe launched and they kept him on.

Large private VC backed companies also don’t always fall under the same rules as public entities. Generally there are shareholder thresholds (where insider/private shareholders count towards) that in turn cause some of the general Securities/board regulations to kick in.

That's not how it works. If you have a conflict of interest and you remain on a board you are supposed to recuse yourself from those decisions where that conflict of interest materializes. You can still vote on the ones that you do not stand to profit from if things go the way you vote.

The decisions will stand assuming they were arrived at according to the bylaws of the non-profit but he may end up being personally liable.