To be fair, he does have somewhat of a point there.
It’s much, much harder to get Oxford alumni to donate money from a friend who works in Oxford’s development office.
Part of that is probably that the funding model is completely different so alumni don’t feel like there were others who ‘paid’ their way as opposed to government paying their way.
In any case, most donations at elite US universities come from a handful of donors every year.
The vast majority of donors donate a very small amount and a tiny minority donate big amounts.
So if Harvard is getting a $1 billion in donations in a year, most of that is from large donors donating >$10m.