"Nothing" to do with rejection of 2E by 1E fans seems a little hard to support. The factors you cite as alternatives don't seem to line up with the sales chronology. Vampire didn't come out until July 1991, Magic at Gen-Con (August) 1993 and didn't do really big numbers until 1994 (though the 1993 sets did sell out almost instantly, Alpha and Beta together only were about 10mm cards total, and Unlimited's 40mm didn't print until December 1993).
We know the big crash in 1980s D&D sales and the
end of the fad was in 1984, and appears to be due to market saturation, with some impact from the Satanic Panic encouraging big box retailers like Sears and JC Penney to drop D&D.
2E's biggest sales year was when it released in 1989, with a big drop in 1990 and a mild
uptick in 1991 and 1992. A small dip again in 1993 followed by a mild uptick again in '94 and '95. 1989 sales of the three core books weren't terribly far below 1980 sales of the 1E core three, but 1E's had three huge years in '80-'83, and '79 wasn't that far behind. 2E never really did big numbers after the release year, at least relative to 1E and Basic's high points.
I'm not going to dispute that Magic and White Wolf had
some impact on D&D sales, but they definitely weren't part of the picture in 1990 when the big drop happened. People aging out and dropping the hobby has been a thing through the whole history of the game; do you have any particular reason to think 2E's release saw more of that than other times?
Eyeballing Ben's chart of AD&D sales over time it looks like the 1e PH (for example) sold about 1.5mm copies over 10 years ('79-'88), vs the 2e PH around 960k over 10 years ('89-'98). And Ben's missing the entire sales of the PH in its release year, '78. I don't have a lot of hard evidence to support the idea that 1E players rejecting 2E was THE major factor, but I think certainly it was a significant one. Like with the '84 crash, some of the issue was market saturation. Folks who had bought as much game as they needed/wanted and weren't interested in getting on the continual update treadmill with the fanatics like me and you.

Whether they rejected it out of acrimony or not, it does seem clear from the numbers that a significant percentage of folks who owned 1E didn't bother picking up 2E.