So true but I'd like to add: amazingly innovative producer (George Martin) and brilliant engineer (Geoff Emerick).
Without those two guys the Beatles recordings might have been just ordinary.
Interestingly, the fiddling by Capitol Records might have contributed to their success early on (when they weren't destroying the intended album track sequence) - for example I prefer the US mono version of I Want To Hold Your Hand over the English version.
I happen to be in Liverpool today, and I have just noticed that the Neptune Theatre has reopened as the Epstein Theatre, and that there is a play about Epstein on soon.
And: it'd be kind of awesome if modern boy bands had to pay their dues playing adult clubs, first. Shame that isn't part of their legacy.
Edit: I should add that I think there's something to be said for the idea of hitting that sweet spot of timing where you're not the first to do something, but you also didn't come along after everyone and their dog did it. Executing well just as the relationship between the category and a much wider audience reaches a certain viability. What springs quickly to mind–forgive me that these aren't defended, or if they're just lousy examples I'd retract upon even a little bit of thought–perhaps Facebook, Nokia's early-2000 phones, the iPhone, the iPod, Rock Band, and so on. Not the first in the space, but they executed well enough (often even better than that; I'm not saying all of the above executed only well enough), just as the category was finally becoming mature enough to fan out beyond its original market, with the product even perhaps hastening that expansion by virtue of the quality of execution.
That is to take nothing away from the strength of the product, but the strength of the product also shouldn't take away from the effects of ideal timing. I think many die-hard fans of anything would have a knee-jerk reaction to saying that lucky timing played a big role in that thing's success, but it's probably reality, and should also be OK to say without people assuming you're denigrating the thing in question.