Think you're missing the big picture here. Sam Altman isn't an "easily replaceable employee" especially given his fundraising skills.
One can imagine Microsoft, for example, swooping in and acquiring a larger share of the for-profit entity (and an actual seat on the board, dammit) for more billions, eliminating the need for any fundraising for the foreseeable future.
If a lot of top engieers follow sama out, now that's a real problem.