"Crypto Scheme": a decentralized pseudo-Ponzi scheme.

I like it.

Digital tulip bulbs

Its certainly a reasonable comparison. But the important thing to remember is: There are plenty of highly marketable, valuable assets that have disproportionately little productive or utilitarian use-case. Fine metals, gems, art, high fashion, etc. People would certainly buy tulips as a fashion or aesthetic item; they have/had roughly as much utilitarian value as a diamond ring.

It was a mania in retrospect, because it blew out of proportion, but there's nothing intrinsic about the asset which would have made it deterministically, conclusively obvious to a knowledgeable investigator that a crash was in-bound (beside, maybe, its biological nature; biological investments are irregular). Rather, it was unsustainable because of the price; but what price is sustainable for tulips? What price is sustainable for bitcoin?

Markets are very, very weird; probably because human behavior is weird. An undeniable axiom: Markets can remain crazy longer than you can remain solvent. And at some point, a "crazy" market isn't crazy; its just the market. Many would say that a $10,000 engagement ring is a crazy asset to purchase; yet thousands upon thousands are sold & resold every year.