Why should a company that is doing a public service for the rest of us, at their own expense, pay more than it needs to to do that service?

If Cloudflare was to behave rationally, it would simply pay the troll to go away. Trolls are very good at making that the logical choice, which is why virtually everyone else just pays up. Cloudflare fights because the act of taking a stand fits with their values.

You're clearly not civic minded enough to appreciate why Cloudflare does what it does. And so you don't understand why other people, who share Cloudflare's values, would be motivated to help them accomplish their good deeds.