2. There is some value to Blockchain technology, so the value is not $0.
3. When comparing, given all of these assets had a starting value of effectively $0 at launch, you should probably look at them from an angel investment PoV. Peter Thiel got similar returns when investing in Facebook.
I'm not saying crypto is (entirely) comparable to Facebook in value (it might, it might not -- too early), but that's how I think the gains could make sense. It's valued like an internet startup, and then some.
4. The global market is still tiny? The entire crypto space is $550bn in market cap. Facebook is $552bn in market cap.
Valuations have probably gotten ahead of themselves and a lot of the smaller coins will die eventually, but it's still a blip in the grand scheme of things.
5. There is too much capital in the world. Too much cheap debt. Too much free money. This will fuel the mania. You could have put $2m in the stock market in 2008-2009, and if you used leverage in a smart way, could have ended up with $75-100m.