1) Elon is not stupid. Despite his 'energy' rhetoric and dubious interests. It was in his own self-interest to buy Bitcoin by the billions… and he did, for Tesla and for his personal wallet.
2) Tesla has profited from Bitcoin more than from the sale of their cars.
3) He now is selling 10% of his Tesla stocks. He will have billions in cash.
4) He will use part of it to pay taxes.
5) Elon hates cash. He knows it burns (loses value) daily with inflation.
So… what is the logical thing to to with those extra billion in cash?
Yes… he is very likely buying more Bitcoin for his personal stack. I would bet my left nut in that.