But we don’t know that megaspeed did that. Right now, it looks like they rented compute to Chinese entities. Which is legal.

Sure. But they absolutely were authorized by Nvidia to buy them for their Southeast Asian data centers, some of which actually even have existed.

What do you expect Nvidia to do, post armed guards in Asia to make sure the GPUs don't move around? He sold to an eligible entity. Unless he had foreknowledge they were planning to smuggle the chips, he shouldn't have any responsibility for what happens to them.