You also have the verification happening in the right place. The person who maintains the Arch curl package knows where they got it and what changes they made to it. Some central signing authority knows what, that the Arch guy sent them some code they don't have the resources to audit? But then you have two different ways to get pwned, because you get signed malicious code if a compromised maintainer sends it to the central authority be signed or if the central authority gets compromised and signs whatever they want.