You know, I was recently struck by a problem with the "fragmenting their own fanbase" part of the narrative. If your problem is that there's so much D&D material on the market that fans aren't able to keep up with all of it and are thus becoming distant from each other . . .
. . . then what are you doing creating an Open Game License that is going to absolutely
flood the market?
Now, there are two possible explanations.
1) The problem wasn't too much product on the market as it was that TSR was generating products that had too small a fanbase and thus too little return for their investment; or
2) The persons behind the OGL assumed that Core D&D was so powerful that, if you didn't counter it with the might of 'official D&D' products that took away from it, everything would by nature adhere to the core D&D playstyle.
I incline towards option 1 with the "fragmenting" bit being an attempt to sell D&D players on "See! All those settings you loved weren't just not worth our while, they were actively hurting the game! You
must accept the Great Purge and the narrowing of the vision! One System! One Setting! One Campaign!"