Cloudflare Workers aren't running Node or Deno though, they just use the V8 runtime and implement a few web APIs (this is oversimplified of course but you get what I mean)
Developing the worker in Deno brings you the benefit of first-class support for typescript and ESM-modules in your worker, and no need for Node polyfills.
Once you deploy your worker, it runs like any other javascript worker on the magical Cloudflare V8 worker runtime.