Comment by mwwaters

OAuth first and foremost is driven by getting secret information from, let’s say, Big Company. It’s understandable that there are many steps for some random Joe to get Google emails or Facebook DMs.

OpenID piggy-backed on it by layering on new terms to an already complex scheme. The precious, secret information from Big Company in OpenID is just Email and maybe Name and Profile Picture. Then there’s a lot of ceremony for the service using OAuth to securely get that big secret (the user’s Email, which they had to supply in the first place directly to Relying Party).