Wikipedia indeed has some unique aspects that give it additional resilience from hostile takeovers, such as public auditability (via edit history etc.), forkability, and finally the fact that the bureaucrats have unusually little leverage over the lives of those who do the actual mission-aligned work.
But universities also enjoyed some unique protections (tenure etc.). The end result was that it just took a bit longer.
So what would you give your money to? inb4 typical homeless/war/refugee charity. People give money to way greater evil than Wikimedia. For example I myself bought expensive as shit coffee (not even worth the price) twice for the past 2 months. It's an overpriced garbage that I regret buying every time, but I never donated to Wikimedia either. I am sure you and many others share the same experience.
With regards to money, they can put all that to an investment company or something and continue to make more money. Why not? So far they have much better track record than any other organizations/companies that I can think of.
Unless someone here really thinks it's important for Wikipedia to pull in 9 figures in grants and donations, I'm not sure there's as much to argue about here as it seems. Organizations expand to fit their budget constraints, and fundraising success has expanded those constraints for Wikimedia. Seems straightforward.