Why would that happen? Simply because the market would have big doubts about the survival of Amazon and here of Ethereum.
Everyone would say that if Vitalik Buterin is selling all his ETH, he knows about something serious that we don't know about.
Vitalik Buterin, like Jeff Bezos, has no interest in doing this. Worse, he would be forever hated by the Ethereum community and could do nothing in the cryptocurrency world.
It is not in his interest to do this as it is for Jeff Bezos with his Amazon shares.
Of course there are such threats. Vitalik Buterin is the creator of Ethereum, this is his child. Watch a few or a dozen interviews with Vitalik and you will understand that he will never sell his child. As long as Vitalik is alive, Ethereum will continue to grow and this is, in my opinion, the best investment at the moment.