> I always thought that a manager should push product vision at their own level, get and organize resources, and assess the talent as fairly as possible.

LOL, reality is very different. Manager first of all is working to keep his position, second to get promoted. Most of them. For keeping he need to become irreplaceable. For that they create kill zone around eliminating competitors. Working against those with brain, not promoting, giving negative reviews, creating 'cases', taking credits for others job. Making those who can leave. I've seen a lot of this shit. This creates a local depressive shithole. It can go for decades in monopolies and in low competition markets.