I see, but you could have simply made your MobileMe account at the time with your existing AppleID. That’s what I did. So when the shutdown of MobileMe was announced I moved my account to a iCloud account so I could keep my @me.com email address. But my original AppleID is still the primary login ID for all of it.
So my AppleID still uses my personal email as my primary login ID (which since about 2005/6 has been one of my own domain emails so it never changes again no matter what my ISP is) but my @icloud.com and my @me.com email addresses are simply alias login IDs to that same, single AppleID. I can login to my one and only AppleID with any of those three email addresses as they are all aliases to the same AppleID account.
I know none of that helps sort your situation now, but just pointing out that in the history of AppleIDs, it has never been necessary to create a new AppleID whenever Apple has introduced some new online service, or retired an existing service. Although I’ll acknowledge its not always been clear how to just keep one AppleID and use new services, or move on from old services when they’ve been retired (like MobileMe).