> How can you possibly know who's good and who's not? Think of the information they have at hand - what the chain of command tells them. What if the chain of command itself is the problem? Think about how you yourself could protect a bad employee if you were a manager. You could! How can they possibly find the truth?
Senior managers should look at what people are actually doing. It doesn't take that much time. If tickets and PRs/MRs/changes are searchable by author, reviewer, and the files they touch (if they aren't, that's your problem right there) then it takes a few minutes to figure out who did the critical work, and who doesn't do much of anything.
In big tech, I've had senior managers (1-3 levels up) that do this, and ones that don't. The ones that do it are great managers. Under this type of manager, people are usually focused on making things actually work and making projects successful. The ones that don't do it can be good managers, but usually aren't. Under these types is where politics festers and dominates, because why wouldn't it? If you don't let the actual work guide your understanding, you're left with presentations and opinions of others.
When I do this (a few times a year), it takes 10 minutes for the easy cases, 1 hour for the hard cases, and once you do a few of these kinds of investigations in the same work area, you start to understand what the collaborators are doing before even looking at them specifically. So you're talking a few weeks of work for 100s of people. A few weeks a few times a year is not too much to ask someone to spend on their primary responsibility as a senior manager.
Past some point in scale, this does become impractical, I don't expect the CEO of a 10k person company to be doing this. But at that scale, the metrics are different anyways.