I have often thought the same thing and I think the best answer is simply propaganda and that Wittman had the misfortune to be chosen as a kind of "poster boy" and ended up with what we call today a "media profile".
As you say, he was not the top scoring ace but he was a "face" and of course the allied troops on the ground at the time had no idea who he was. Even Joe Ekins who has been made a central character in the story was unaware of him until all the fanfare started after the war.
Not many people seem to have heard of Carius who I believe was of similar type and I think I am right in saying he lived after the war as a pharmacist in a relatively quiet town until he died a few years ago with no ringing of bells at all.
Just my opinion as you asked for. Now standing by for the outraged howls from Wittman acolytes
Still it is good book fodder eh?
Regards
Mark
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