OP, the same that caused the dump of the dotcom bubble? But would the reasons "why" matter to you today? They won't, right? All we saw was the crash weeded out the bad companies and left only the good, like Amazon.
Perhaps that is just what we are doing right now, weeding out the crap coins. I can't imagine institutional money getting into shitcoins for the reason that they are shitcoins. They will see through the bs, and I don't think we are gonna experience anything like 2017 ever again. The coming out party is over it seems, and we gotta align our sights in a reasonable and realistic fashion from here on out. Shitcoins are gonna die soon, try not to have too many of those in your portfolios.