Google is not a charity, but their core business - Search - depends on the web having content they can index. This is a play to defend their existing business, not a revenue opportunity.

I think AMP is a good thing for the mobile web. It makes web pages actually usable. People get a bit wound up about the fact that Google hosts the content on their CDN, but there is always a real URL backing it, the content isn't locked into Google's platform.