Incredibly hard. If there were some formula and it was really easy to just keep "the good ones", then every company would only have great managers. It's simply not that easy at scale.
It's amazing how many smart people here think this is just a trivial problem that they can solve for big tech if big tech would only listen.
This is a fundamental human organization problem that many countless organizations of people have failed to perform optimally since people have started organizing into groups.
Listen to yourself. That's what management is supposed to do: manage people -- including other managers. You can't both accept and deny responsibility in the same breath.
If you truly believe that, then this is cognitive dissonance in it's highest form.
There's what you imagine and what you can see with your own eyes in reality.
Amazon, with its billions and hoards of smart people, still ended up in a situation where they find themselves in excess of 14,000 employees.
It means that there's no simple formula and perhaps once in a while, orgs just need to clear the slate and see where the pain points are and build up once again.
Listen to yourself. It's management's job to manage people. Some of those people are going to be managers. So management can't police themselves apparently?