Iosue
Legend
Dancey didn't anticipate a Pathfinder because it never occurred to him that WotC would ever make more than incremental changes in a new edition, i.e., that 4e would be as close to 3.5 as 3.5 was to 3e, or as close as 5.24 is to 5.14. Level Up and Tales of the Valiant demonstrate what he expected: even someone who republished essentially the same game, with some unique quirks, would be unable to compete with the brand name power of official D&D. Of course, WotC then and went with a completely different system altogether incompatible with the one licensed by the OGL...Interviews with Dancey suggest he considered it and did not care (that's why the d20 License existed) but he was also out long before Pathfinder made it a real thing. In either case, I think you are right about DMsGuild being similar in the support way but providing WotC more control. I legitimately wonder who came up with DMsGuild. It was a smart move and many other companies have followed suit.
As for who created the DM's Guild, I believe it was the brainchild of Chris Lindsay, one-time D&D Product Manager (he got hit in the Great Layoffs of 2023).
As for the Rules Glossary, my take is that the PHB has been fundamentally redesigned for two things: a) to get a new player familiar with and playing the game without having to read the whole book, and b) act better as a table reference. In the GenCon retrospective, Mike Mearls made the very good point that the biggest group of players is not those who have just the PHB, it's the players who have nothing, and borrow a PHB from someone when they arrive to play.
As a veteran player, I can appreciate the design intent, even though it is not necessarily what I need or want.