Well that doesn't make a lot of sense, aside from the use of crypto.  If banks (all of them) collapse, there's not going to be much cash to go around--not that I think any scenario like that is imminent.  Maybe at some point in the next few generations, but now?  Nah.  The world economy is in much better shape than you seem to think it is. 

This has been the topic of many threads, by the way.  If there was a global catastrophe that put the use of fiat in jeopardy, it's more than likely that there's going to be more than one currency that's still stable, and that's what people would turn to waaay before they started using crypto to buy stuff.  Look at Venezuela or one of the other countries that experienced hyperinflation; they started using the USD or a neighboring country's currency, not crypto.

And by the way, I've been waiting for a stock market crash for years and have written that in a number of posts....yet it never seems to come.  Bull markets can go on for a long time, but what we've got is just goddamn ridiculous.  And with interest rates starting to drop, I can't imagine that won't entice the high-rollers to start using more leverage in their investments.  Crazy-ass times we're living in these days.