And you can bet those who bought at $1 sold all they had at $10 ("wow, it's like 10 times what I invested, this is insane, this probably won't go any further!"), those who bought at $10 sold everything at best at $100, those who bought at $100 sold at $1000, etc. Actually, I'm not sure the people bitcoin made rich are that many. I have yet to see an article explaining how someone got millionaire by getting early into bitcoin.

As for fundamentals, the underlying value of cryptocurrencies is to be a store of value that is not as easily stolen than cash, while still not sitting in at a bank. You can see it as cash that can be transmitted over the network, in small or big amount (and quite fast in that case, comparatively to a wire transfer). Of course, whether this tech will become mainstream is yet to be seen, it can still fail. On the other hand, the company you bought stocks from can also bankrupt and close.