Main difference is that blockchain never had an actual use case (speculation doesn't count) beyond buying heroin and running ransomware. Machine learning had practical applications for years that nobody really thought much of at the time, and the marketers got a hold of it after it was fairly well established without them and right at the point of a massive wave of breakthroughs in the area.

That being said, there is a fucking massive AI bubble. A large portion of the things we're seeing will survive when that pops, but boy are there a lot of very overconfident investors who are going to get burned hard on this.