but then how did super password last for so long, with more and more of the local stations were beginning to do newscasts at noon?
Perhaps the other networks were "encouraging" their affiliates a little harder to do a noon newscast.
The Cleveland NBC station was an O&O at the time and so they carried the entire network offerings. It wasn't until they sold their O&O (IIRC, to Metromedia) before they began doing a noon news. By that time, SP was already gone from the daytime schedule. The ABC and CBS stations in Cleveland always had noon newscasts going back to at least the early 70s, while the shoestring-budget ABC channel in Akron never did.
Toledo's NBC affil had a noon news for quite a while by that time, so the noon programs were never seen there. (However, 12:30 programs, like Wordplay, were still seen).
I don't recall the NBC affilliate in Detroit airing a noon newscast, so they most likely aired SP.