How are you instilling that attitude in your company? How big would your company need to grow before misguided middle management might be appointed who _does_ think this is an appropriate management technique, resulting in this happening on your watch with you later described as a "detached executive"?
Having stuff like this "never even occur to you" leaves you in the possible danger of not being aware if it starts happening around you. (Though, in this instance, the revolving door developer role should have brought some scrutiny on the manager in question…)
The startup described by the OP is smaller than our company, and they already have this problem. If we were large enough to need middle management, I would be absolutely paranoid about hiring good people that understand management. There is a lot of culture around hiring good engineers and sneering at management, but it seems to me that hiring good managers is an order of magnitude more important. A bad engineering hire can be a very expensive mistake, but a bad management hire can be absolutely devastating. They can derail their own team, and a few other teams they interface with.
If I had a really insecure/misguided manager like that reporting to me, I cannot imagine not noticing. Here's one simple trick to do that -- have occasional one on ones with their reports. Most people won't necessarily say anything bad about their manager directly, but you can quickly gauge people's sensibility in what they don't say. It's like doing reference calls on hires. Few people will say "this guy wasn't good" but there is an enormous difference between references who say "this guy was ok" and "this guy was spectacular". You can sense it very quickly if you're looking out for it.
Also, I would advise against not having 1:1s with your direct reports' reports. To a new manager, it can feel like you're undermining them and don't trust them, and to an individual contributor it can make it very confusing who they should bring ideas or concerns to.
Instead, hold informal lunches with a subset of individual contributors without the manager present. This is a great way to get them to know & trust you as a leader, and you can still gauge the tone of their happiness from how they react at the lunch. You also sometimes become aware of whole-company cultural or organizational problems this way, things that really need a founder/CEO's intervention to get fixed. And if you pull the subset from across different teams, it also serves as a way for people from across different teams to get to know each other and strengthens social ties between different areas of the company.
That sounds like "360-degree feedback":
Which seems like a good idea but I've known of places that turned the entire process into a process that sounded like something from the Chinese Cultural Revolution - where all managers were ritually had their characters attacked by everyone surrounding them (usually to the point of tears).