My dad worked his way up to middle management in a large railroad.
Management and executives had almost all worked their way up the ladder. Toward the end I think some of the higher-up ones were encouraged to get an MBA as they advanced, but they didn't do much hiring of MBAs.
The company got bought by another in IIRC the late 90s, and this other one had already been taking over by the "professional managerial class", and they quickly replaced most of the folks from the top down to the layer just above him with their own sort.
His description of what followed was incredible amounts of waste. Not just constant meetings that should have been emails (though, LOTS of that) but entire business trips that could have been emails. Lots of them fucking things up because they had no idea how anything worked, but wouldn't listen to people who did know. Just, constant.
The next step was they "encouraged" his layer to retire early, for any who were old enough, which was lots of them since, again, most of them had worked their way up the ladder to get where they were, not stepped straight into management as a 25-year-old with no clue how actual work gets done. I haven't asked, but I assume they replaced them with a bunch of young business school grads.
There are sometimes posts on HN suggesting that our dislike of business school sorts is silly or overblown, but if anything I think it's too weak. The takeover by them and, relatedly, the finance folks has been disastrous for actual productivity and innovation. Companies should be run by people who've done the work that the company does, and not just for an internship or something.