They're honestly not doing much at all. These are quite cushy positions. Work usually gets sloshed around and offloaded onto staff who make much less but work much more.
For example, at my public law school (1,000 students), there was the dean (who many suspected had an alcohol problem and appeared drunk at commencement) who makes $330,000 per year. His job is to just go around the country/world selling the school to "recruit" (we don't actually need more faculty) in order to boost our "prestige" so we can climb up in the almighty US News rankings. He doesn't engage with faculty or students at all.
Then below him is another Dean, who is a prick. He makes something like $280,000 and also doesn't do much at all. He is also a "recruiter." At least he answers emails when you have a question.
Then there are other Deans, like Dean of "Student Affairs." She makes $130,000. Mind you this is just for a law school of 1,000 students situated on a larger university campus that will have its own Dean of Student Affairs as well. I have no idea what she does. She does get dressed up every day in fashionable clothes and walk around the building chatting up people. That's all I ever saw her do.
Below that is the "Director of Student Services" or something like that. This guy works his ass off, has a mediocre basement office, but literally runs the school. What does he earn? $80,000. Anytime anyone had a question, they had to go to him. After exams, he gets a pile of USB keys, one for each exam. Takes each grade for each class and logs it, curves the grades, reports them, etc.
It's all a big scam. A big one. Tuition at this school has risen every year -- they want to build a new building (Why does a law school need a fancy building? All you need is a room and a professor). They think it will boost their "ranking." Nevermind that "ranking" doesn't do anything for the local job market, which is still stagnant, and every year new graduates enter it looking for work to pay their $150,000 in loans (at 8% interest, non-dischargeable).
This school isn't even that bad compared to the other law schools out there, namely the private ones. Even a top school like Columbia states on its own site that students will spend $250,000 for their law degree (this includes a conservative housing budget).
The only thing more mind blowing than the scam itself is that we all sit around and don't seem to care as these people eat our young alive. In fact, they worship these institutions. It's their "alma mater," after all, it's like family, isn't it? Some even DONATE to them! The federal government enables the scam by flooding the industry with easily obtained credit, with no restrictions on tuition charged, and even letting for-profit "schools" get the money if they want.
This is a racket that is in big need of disruption. Where does it start? Perception. Once we stop perceiving these degrees as meaning anything, once we stop valuing prestigious names as absolutely required, and look more at individuals themselves when hiring, the racket will die.