Gygax was writing at a time when "campaign" often meant something rather different than it does today. A Campaign was a shared world, which may be played in by dozens of players over time. Putting a half-dozen of those players first may have impact upon a dozen others - sometimes the needs of the many may outweigh the needs of the few or the one.
I know what Gygax had in mind, but I think even in 1979 that was probably a minority way of playing, and within a year or two, when Moldvay Basic came out, I think that it was cetainly a minority way of playing.
More generallly, though, I think that Gygax is emphasising the integrity of the GM's creation over the experience of the players. That's not unreasonable or anything - it was debated in the letters pages and articles of the magazines of that time, and it continues to be debated on these boards today - but it's not a position I agree with.
I think you're reading "the game" with a prejudice. I don't think he meant "the game" to mean anything related to TSR's commercial interests. Since hes talking about the DM going outside of the printed words in the rulebooks, that seems pretty evident to me. He is being a tad pretentious, perhaps, but he's trying to put the DM in a context where they wouldn't as easily get pushed about by players - the game, the long-term thing the players and DM share, was to take precedence over anything going on in a particular session of play.
You may be, probably are, right about that. Though I think there is also a heavy emphasis in the AD&D books on the virtues of "official" rules and the threat posed by various alternatives (eg the attacks upon variant combat and spell systems sprinkled throughout the books). I don't think Gygax is clearly distinguishing "the game" as an individual groups play experience and "the game" as a commercial offering from TSR in competition with other systems like T&T, C&S etc, which he clearly is arguing are inferior.
All I did was post the words of E. Gary Gygax. I'm not imposing anything.
Well, in part I was being ironic - or, rather, pointing to what I take to be an irony in giving such forceful instructions about how priorities
should be ordered in a passage that tells the reader to prioritise the spirit of things over the written word. (By contrast, when Moldvay talks about "guidelines not rules" he doesn't then go on to say how things
should be.)
But I did take your post to be an endorsement, to at least some extent, of Gygax's passage. Otherwise why post it without further comment?