The reason is that people keep making the same mistake, because people are not very good at assessing high-risk, high-reward projects.

Only a real deadline/delivery failure can wake people up, and only if they haven't pivoted their dream to something else, and only if you don't have other people knowing it's a scam, but willing to prop up the stock price because they are highly invested.

Scams, like cancer, are real; they survive, grow and defend themselves using the same mechanisms (laws, advisors, promotors) as ordinary investments/tissue, until they kill the patient -- so the best scams target the largest unkillable patients and enlist the broadest and deepest range of self-interested insiders as their defense.

It's beautiful, if you really think about it, as a tragic example of the worst of capitalism.

So you are never going to convince people that Tesla won't make a fortune on humanoid robots or SpaceX won't colonize Mars. The fever will break when people decide flying robots (or whatever) are a bigger business then humanoid robots or some other company than Space X will colonize the ocean before Mars. You aren't going to convince people to price these things reasonably but eventually the heat will wear off.

As more and more wealth get distrubuted to fewer and fewer hands, and as fewer and fewer extremely rich individuals control more and more of the market, My gut feeling is that if the market was ever rational (which btw. I am not entirely convinced of) that very much no longer holds true.