Most companies fail to hold managers accountable.
There are several reasons for this. Managers of managers don’t pay enough attention to what’s happening under them. They can understand results: is this team delivering on what’s expected? But, more often than not, they have no clue if people are satisfied with their role. An effective way to get around this, is to do skip levels 1:1s. They can provide a window to what’s happening in the lower ranks. But this requires time and discipline. Managers of managers are usually worried about other things, unfortunately. Even when they are aware of poor performance, they might not be willing to do the right thing. I have witnessed this multiple times throughout the years: a manager doing a bad job and their manager not acting. Just like an IC doing poorly and their manager not doing anything about the situation.
The most basic measure of success for a manager is if their attrition rate is well below the company’s average. This gives a good idea of how well they are doing their job. Hiring people is tedious and expensive. Losing people because of a manager’s poor behaviour should raise quite a few red flags. Another metric is how well their team is performing. And you can probe if they are delivering on time and with quality. If that’s not the case, why is that? If there are poor performers inside that team, the manager is still accountable for that. Either by up-skilling them, coaching them or via more drastic measures - usually via a performance improvement plan (PIP). Moreover you can also check how often people want to leave their team. There might be good reasons to change teams, like being bored and wanting to try new things. But it can also mean that their manager is not doing them any good.
Another way to collect qualitative and quantitative feedback is to use tools like Peakon. They provide managers a good framework to understand where things are going poorly. It also shows the team's morale and other things that might be bothering people. This information is all anonymous, so people can be honest about what’s going on. After a certain size (~30 people) these sorts of tools should be a requirement in any company.