Most companies don't even hire management positions from within anymore so pretty much everyone is just learning leadership on the job. It's rare that anyone goes out of their way to mentor people or set them up for promotions in most lines of work.
One of the companies I worked for cleaned house at the leadership level and several others jumped ship. Most of the new managers had very little experience in the role. Their credentials were great, but they had a steep learning curve and leaned on their subordinates to understand the job.
It was an odd experience. On paper the new managers looked great, in action they were silent and non visible. We'd have department team meetings you'd only hear the managers that were always around speak.
I've been fortunate to have mentoring relationships at a few of the companies I've worked for and it's served me to survive some of the poor companies I've unfortunately had to deal with.
I try to pass that knowledge on to younger employees whenever I get the opportunity. If you stick around long enough to understand why they hired you, that's half the battle. Your role is often bigger than your title.