Every market cycle develops a story powerful enough to persuade investors that old valuation rules no longer apply. In the late 1990s it was the internet. In the mid-2000s it was housing and credit. Today it is artificial intelligence.
The story is not false. Indeed, that is what makes periods like this so dangerous. The internet genuinely did change the world. Housing was a real asset rather than a speculative fantasy. Artificial intelligence is almost certainly destined to transform large parts of the economy.