How did Tesla sell their Bitcoin?

Serious question, and I'm really curious if anyone has an idea: How do you sell 1 billion dollar worth of Bitcoin?

I imagine that there is this guy from controlling, checking the Coinbase wallet address twice with sweaty hands, before he transfers Teslas billions to there, before he cashes out.

Of course this is highly unlikely but seriously, how do you manage to sell such a huge amount of BTC? And especially, where? Are banks involved in any way? This would make sense when it comes to so much money but otherwise I also doubt this as we are speaking of crypto and not fiat money.