I recently moved my domain’s DNS and CDN to Cloudflare, and I noticed that all I had to do was to get my domain registrar to change my NS records to point to Cloudflare nameservers.
My question is, how does Cloudflare know that I’m the real owner of the domain creating the account and attempting the move, and not someone else? If someone else had created their own Cloudflare account before I did and also attempted to move my domain’s DNS to their Cloudflare account before I did, would Cloudflare have given me an error when I’d try to do the same thing? If not, would Cloudflare have given us the same Cloudflare nameservers to point to? What would have happened?