This is exactly the kind of one-sided perspective that makes me very sceptical. No, they didn't 'leave fiat' in any way, and they never will. At best they can hedge against it a little. But while that might be personally profitable, it is not clear at all whether it is a net benefit; the main problem of western economies nowadays seems to be too tight monetary policy, and crypto is tighter than fiat.
Is not cryptocurrency the ultimate fiat currency?
It only has worth because we all "agree" it does via supply and demand for the currency itself, rather than any backing material value. Aside from a bunch of power plants in China, I suppose? But people don't hold Bitcoin at $20,000 because they strongly believe in the material worth of the rural Chinese electric grid.
(post edited to say "fiat currency" rather than the noun "fiat" which means decree or command)
I did not mean the bare word "fiat", and will update my post accordingly.
Whether millenials have learned about existing financial systems or not is immaterial. It's unlikely they'd be holding a position in bitcoin if it weren't for the massive gains that have been seen in the past year. It's purely a get rich quick play for the majority of buyers today.
A lot of millenials have learned a lot about the existing financial system due to Bitcoin, even if it was initially to make a quick buck, and I suspect there's no way back to fiat for a lot of them.