I think he may mean that the exuberance going on right now in the crypto and nft markets may be seen as a "top signal" predicting a market crash soon (people moving into riskier and riskier assets usually precedes a crash). Timing the top of markets is hard though - and while the music is playing you have to dance.

Oh, it most certainly would; it would wipe out billions of dollars of what many people consider part of their wealth. Joe Cryptomillionair spends more of his regular income because he feels rich because of the balance in his crypto wallet, and thus stimulates the economy. Wipe all that out and suddenly a lot of people who were spending a lot of money are scrambeling to pay their morgages, perhaps even having to sell other investments to do so.

There have been a ton of them and it hasn't even come close.