Same reason they don’t step in to save the SF Opera or the Met: these are fully bourgeois capitalists who have shed even bourgeois self-consciousness. They feel no obligation to justify their wealth, so they spend it on being internet famous instead of colleges or the arts.
I think it’s rather interesting that despite being far wealthier in absolute terms than a Vanderbilt or Carnegie or Stanford, and being directly positioned in an industry that could benefit from it, no tech elite has ever founded a university, and few have even given endowments