Why would there need to be a limit? Do you imagine that Harvard having a large endowment is somehow depriving others of money? If so, you are fundamentally misunderstanding - endowments are invested in the economy.
A nonprofit institution doing good work should always seek to expand its reach and the extent to which it fulfills its mission. Are you concerned that the American people are too educated, or that too much is invested in research?
Currently, the incentives are to (a) give the fund administrators nice big bonuses, (b) increase the wealth of the organization, and (c) give the donors a kind of lingering life after death from their bequest, thus lots of strings and clauses.
The thing that's missing in this is progressing the goals of the organization itself, its mission.
Universities shouldn't be hedge funds with a sideline in teaching and research.
Increasing the wealth of the institution and giving donors life-after-death are both about serving the goals of the institution. I agree that excessive management fees can be a problem, but universities aren’t selling shares. The hedge fund’s gains serve the university’s mission, not to enrich some investor.
Universities shouldn’t be fundraisers and lobbyists with a sideline for teaching and research. Becoming independently wealthy frees them from that.
A nonprofit institution doing good work should always seek to expand its reach and the extent to which it fulfills its mission. Are you concerned that the American people are too educated, or that too much is invested in research?