TES Fans had to wait longer this time, while Bethesda made Fallout 3. The wait must have just became unbearable, so crazy breeches started popping up.
MW3 being released on Tuesday helped this, as so many retail stores don't ask folks to read... just stock shelves.
So many stores genuinely thought TES came out Tuesday with MW3, as a competitor.
If you've already got a consumer in the shop buying MW3, and have a chance at selling them Skyrim at the same time, or not having the chance to sell them skyrim (since they would be less likely to return to the store only a couple days later), then you put skyrim out on the shelves and try to sell it.
Financially, it seems to make sense, unless there is something in the contract that could bring fines to the stores or corporations that do it, which I would have to doubt really.