when you start out in a gaming environment where the only games being played are AD&D 2e and Vampire, the "DM as God" concept is pretty hard to ignore. My own exposure to the local gaming community during high school and college, as well as the nascent online communities of the time, was that the "DM force to make the story go" was the convential wisdom of the time (the mid to late 90s).
I started GMing for my university group in 1990. The five of us in that group met as players in a 2nd ed AD&D game, but after two or three sessions sacked our GM for railroading and reconvened under my GMing. The game was Rolemaster. The players were D&D players, raised on 1st ed AD&D, plus one had a bit of RM experience. (I had played one session, loved it, and bought the books and taught myself the rules so I could GM it.)
So for us, the idea that GM force could be pretty toxic was well established.
The next year, I recruited a couple of further players for the group were also seeking refuge from excessive GM force in a 2nd ed campaign.
The idea of "GM as god" was never one that I got from the AD&D books I'd read. (I never learned about the 2nd ed text until I visited the Forge over a decade later - I used to play 2nd ed but relied on my 1st ed rules knowledge plus general familiarity with AD&D practices.) And it was certainly widely enough doubted that I was able to build one of the longest-running uni groups out of refugees who wanted a different sort of play experience.
This isn't contesting your experience, of course. Nor your claim - which I agree with - that 1989 didn't just turn up unheralded with a brand-new set of GMing advice. I'm really just reiterating the point that playstyles were diverse back then, too, and in all my exposure to D&D - rulebooks, magazines, messageboards, usenet etc - I've never seen any generally shared assumption that the GM is god. Playstyles have always been diverse.
In other words, you ignored the part you disagreed with.
I ignored the part that I assumed to be a legacy intended for some other playstyle. The game advertised itself as "back to the dungeon", and I took this seriously, and so ran it more-or-less in the spirit of classic D&D (I ran Castle Amber for around 6 or 7 6th level PCs) - which is not based around "DM as god".