There should be a mechanism to address the manager leadership vacuum. Many are simply not doing their jobs and are unqualified to have people responsibilities. In 2007, Ford had a headcount reduction phase where they walked out only managers. It was only 1 day but LL6 to LL2 were impacted. The numbers were not very large and a few good managers were impacted as well as some toxic managers.
Some managers hitch a ride on the visibility train by inserting themselves into projects when they start to have traction. Claiming credit for the work of others is a frequent ploy.
Good managers are few and far between.