> this assumes Musk is acting rationally

No.. it assumes Musk is only trying to maximize his net worth with this move, which is a ridiculous assumption.

At the point where he's at, what exactly is rational? It's all up to what he wants to achieve. Money is not the end goal for anyone. It's what you want to do with the money. What does he want to do? Only he knows but my guess is influencing the world towards what he believes is better. Twitter seems like a interesting tool for that.

If I was drinking coffee I'd need a new keyboard.