To the extent that this trope is true, it will usually be as a result of the non-lethal form of The Firefly Effect, where the studio are trying to boost ratings. There is one other way in which this trope can legitimately manifest, as well.
a} An initial film (The Matrix being a good example, as was Cube) is released, which the releasing studio does not expect to be a mainstream success. Because the initial film is only expected to appeal to a niche audience, the storyline will often be more intelligent than usual, and the producers very often won't resort to the usual cheap gimmicks (excessive nudity or rather large explosions unless those are genuinely in context with the storyline, etc) which are intended to draw in large audiences.
b} Because of said film's unusual degree of artistic integrity, it will become far more popular than the studio anticipated.
c} This causes a case of Sequelitis in the studio, due to the hope of making more money. Said sequels, unlike the original, not always, but usually will use the usual crowd-pleasing tropes mentioned above, as well as re-tooling the original film's premise to appeal to younger audiences.
This elitist tendency essentially turns Fandom into a speculations market — if you like it before it's popular, or if you hate something because it's popular, only then does your profit margin in coolness points amount to anything when you fling away your shares in the fandom in horror of the masses. (Incidentally, note the jargon here. "Speculations market". "Profit margin". "Shares". Ironic, no?) If it never Sells Out, no one will get the name recognition when you say "I liked X before it was popular." Ironically, fandoms of little-known works almost always expand by word of mouth — the very reason it became popular is that these people kept talking about how cool it was, and enjoying acclaim from being the one "in the know" about a good work before anyone else. (Which they lose when it becomes popular.) For further irony value, these snobs often claim to be X's original and/or true fans — but, in dropping X like a hot potato after X becomes popular, they actually reveal themselves to be fair weather fans (or, if you prefer, foul weather fans), since if they truly were a fan of X, then they would be supportive of X, regardless of its popularity, if it still had the fundamental draw of what made X popular in the first place (however, if X genuinely has abandoned or watered-down what made it popular or liked in order to appeal to a wider audience, then fans are justified in critiquing that decision).
