The current leadership retains power in an IPO. Is there a minimum size chuck one has to sell when IPO-ing? How do you know it will be big chunks?

In one case your ownership is diluted by maybe 10%, and you keep full decision making power and everything else. In the other it is diluted by 100% and you are now an employee. They are very different outcomes.

Sort of. You can do what Zuck did; give your shares more votes, so you stay in control. (He owns 13% of the shares, but more than 50% of the voting power.) That's less doable with an acquisition.

uh... thats exactly why anthropic wouldnt want to be acquired? weird response to that comment IMO

Not necessarily controlling stakes.