Does the concentration of power in the hands of a few ever benefit the majority?

Not inherently. It can hurt. What checks are on power? why is power being centralized? these are the questions you need to ask.
Graeber says, and I agree, that good authority should be self dismantling. Like teachers teach kids and so the kids no longer need them. The teacher stops having authority over that child at some point

Authorities is beneficial about cares and ruled out which it's absolutely and harmed in goods spirits issues is could lead up government decline