Also, they may publicly oppose bitcoin in the media but that doesn't mean they can't quietly invest in it. This is a financial game, the winner is the one who makes the most money, everything else is irrelevant. So I hardly believe anything other people say but instead I like to look at what they do. I wouldn't be surprised if one day people who claim to hate bitcoin end up owning large amounts of bitcoin.
He can just leave someone else in-charge of his BTC investments (a middleman or third-party). Bitcoin spot ETFs prove to be a great way to invest in the cryptocurrency without the need of any technical knowledge. What's stopping Warren Buffett from doing it? Maybe he's already investing in BTC under our noses. We can't know for sure.
Who needs him anyways? BTC can do fine with or without the support of the wealthy. If it has managed to get this far, it can achieve anything. I have a feeling Buffett's children and grandchildren will get involved in Bitcoin sooner or later. Just you wait and see.