Electrical engineering. It happens, especially if you worked in R&D and continued to publish over the years. One of the professors currently teaching me spent 5 years at a startup and came back to his alma mater as an assistant professor. He's an expert on botnets and quite active, so that might be an exception haha!

That is, of course, a very silly cultural thing they'd be better off without. My supervisor spent a decade in industry before returning to academia, and he's a pure mathematician/logician.