I don't actually buy this. Environment makes a difference, sure, but if someone goes off and succeeds technically[1] at a another company in a big way they would have succeeded at yours as well. If that person can't succeed with you, then there is something fundamentally wrong with your organization. My experience, though, is that such organizations have much lower hiring bars.

[1] I say "technically" because it's quite possible that the person is not very good technically, but landed at a place where that didn't matter and some combination of non-technical skills led to their success.