Ok, erm, why would the general audience have been put off and asked „Who is Khan?“, but they weren't put off and asked “Who is John Harrison?“
Exactly. It wouldn't have made any difference.
And yes, the cat was definitely out of the bag before the movie hit theaters. I was one of the ones who insisted for a long time that there was no way they were going to go with so obvious a villain as Khan, and even I
knew before going into the theater that Khan was definitely in it. Online film reviews had spoiled everything leaving no doubt at all.