I'm coming from a CS perspective.

If they are successful at a top university and leave to try other things (usually startups), then they will have no problems going back to academia. Sometimes it is even viewed positively.

For example, right now Carnegie Mellon has been seeing a flock of their faculty leave to go to tech companies or to do their own startups. Other universities would fight over a successful ex-CMU (or UW!) prof to come to their institution.

Depending on their level of success, they may not get back to a top 5 university, but some other R1 university would gladly take them!