Cloudflare operates as a reverse proxy between a user’s browser and the origin server of a website or application. When a user requests a webpage, the request is first routed through Cloudflare’s global network instead of directly to the origin server. Cloudflare then forwards the request to the origin server, retrieves the content, and sends it back to the user.

It is doing that by being authoritative DNS provider and providing useful features in case of attack but imagine that everyone start using cloudflare then it become the authority DNS wise.