Elon Musk has probably taken a big haircut on his current stake in Twitter and is also risking being forced to buy Twitter anyway or losing 1 billion plus legal fees. That sounds like an awful lot of work to sell 8.5 billion worth of Tesla shares.
Well, Musk is not "most people", and 8.5 billion is a small percentage of Elon Musk's net worth. I'd not be surprised if 8.5 billion is perhaps the daily fluctuation in his net worth!