You bolded the wrong part Notice the self-perpetuating dominance. The OGL ensures very few attempt to unseat them and those that could maybe try cannot do so because they do not have the broad ecosystem and get big enough to actually try.Ding ding ding... and it is WotC's brand recognition that allows this.
The benefit to WotC is that it ensures their position in the center of the universe, because it gets constantly reinforced instead of constantly challenged.
the majority only uses the PHB + DMG + MM, so this is obviously trueit has been proven the vast majority of those playing D&D use WotC materials only...
I think they underestimated it, and that is why they changed course. What is your explanation for them changing course thenso when you claim that WotC benefits just as much or more from the OGL as 3pp I think you are vastly overestimating exactly what and how much they gain... I think WotC has a better handle on this and is in fact why they were willing to terminate the OGL... I'd bet it's not benefitting them to the extent hardcore gamers on a D&D focused forum seem to think it is.