Am certain ethereum will crash In the same way, as if Jeff Bezos sold all his Amazon shares overnight. Amazon's share price would plummet.
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.