Harvard's endowment is so huge that they use it for everything.
"Harvard depends on its endowment for about 35 percent of its operating budget, and some of its schools rely on endowment income to cover more than 50 percent of their expenses"
Harvard isn't a trust fund. It is a hedge fund. One of the larger ones. The hedge fund has reported 15-20% returns for five years running.
The hedge fund also has a PR arm with a $700 million a year operating budget, whose main objective is continuing to convince the relevant politicians to continue keeping the hedge fund tax-free.
"Harvard depends on its endowment for about 35 percent of its operating budget, and some of its schools rely on endowment income to cover more than 50 percent of their expenses"
That isn't a 401K, it's a trust fund.