Sure, there are plenty of people with decades of experience who haven't actually developed beyond a mid level engineer. Long stints aren't proof that somebody is skilled. The point is that short stints are a worrisome thing on resumes at some point. Not a hard line - if I've got a personal relationship with somebody or strong recommendations from people I deeply trust it changes things. But somebody coming into a leadership role needs a lot of time to even understand an organization well enough to propose changes, let alone see those changes through.

"Some new director showed up, reorged us, and left" is a failure mode for organizations. It causes huge problems and needs to be avoided.

>Unrelated: today is on the news that Unilever's CEO will be resigning after 3 years, which also seems short to me.

Wait til you hear about Australian Prime Ministers