How did remote work expose that managers are managing people?

The issue I see exposed is rather the top-heaviness of many modern companies where there are too many managers and too few people that do actual work.

If you're a manager and doing low level work you're doing it wrong. Your role is to remove the interpersonal roadblocks, get people to pull in the same direction, inspire with your vision, hire the right people, and fire the people that don't fit.

A manager doing these things properly has value. But that manager has to manage enough people to make these efficiency gains worth more than the manager's salary.

I'd say another role of a manager is protecting the team from external interference and time-draining activities. You don't get to see that side of it as a team member, or shouldn't if your manager is doing a good job.

So much this! Unfortunately instead of keeping unnecessary work away from their team many managers instead delegate the work they don't like to do to their team. Thus they essentially decrease the productivity of their team.

Being a good manager is actually a thankless job, because you have to deal with all the crappy stuff, like keeping office politics in check, shield your team from budget and bikeshedding discussions, order equipment etc to keep your team productive etc..