Before I had an insider’s look at a boarding school, I would have agreed with you about administrations becoming “bloated”. But, looking behind the cutain, there are so many things that have changed, and that now require support staff!
20 years ago, there weren’t IT departments. Now, there are, and they are busy! There wasn’t the need for communications to the degree there is now – there was no social media, no need for videographers. Games were not livestreamed. There was no human resources department, and no avenue, eg, to document sexual harassment-- which has come back to haunt the schools!
There were no administrators focused on the experience of international kids, or poor kids, with the resulting difficulties those kids had to struggle through.
As some schools introduced new and exciting programs – eg buying a farm and producing food for the school – people had to be hired to run those programs.