The AI bubble music stops when one of these former-darling companies has a complete crashout rather than a "successful exit". The investors keep investing because even largely-failed products get acquihire paydays
Note that Meta paid ~16b for Alexandr Wang, and Google paid ~3b for the windsurf executive team. You are making a category error -- the talent pool isn't "ML researcher" it's "competent leader"
They’re buying the customers and the brand.