DNS resolvers aren't that expensive to run. Besides, one of the founders of dns0.eu has already scaled and sold a venture-backed startup (DailyMotion: https://archive.is/4pN5e), and currently employed as Director at Netflix. Pretty sure they can keep paying for dns0.eu servers for multiple decades. The only problem is maintenance, which is automatable to a large extent.

Because I give them money to keep the lights on?

That way they don't need to rely on grants or investors who usually need hockey stick growth and make the business do stupid things.

This is why I used to pay for pinboard (before the admin disappeared again) and still pay for Newsblur.