Really? Yeah, I get that it not being a microtransaction-pile-of-garbage probably helped, but did you play it? Seriously, nobody at the beginning could have thought it was good. After the buzz, quality isn't relevant.
The problem is the ranking algorithms. At least on iOS, the relative ranking list doesn't go below 300, so if you're below that, you're invisible. But, if you crack that, you're off to the races (that's how I stumbled on it).
The bigger problem is that rankings don't decay. Candy Crush should be continually falling in the rankings if it isn't growing in order to make way for something new that is.
However, that isn't what Apple wants. Apple wants things that PAY. So, they want their ranking algorithms to keep the things that gross the most money as high as possible as long as possible. So, Apple isn't even remotely interested in "fixing" the problem.
And we come back to, "The walled garden sucks for the consumers."
I learned about it through a girl I'm currently seeing. She is very far removed from the whole tech scene. Her cousin told her to try it, and then she told me to try it and impress her by getting a high score. So I tried it, enjoyed it (masochism involved here), and the very next day my roommate asked me if I knew of the game. We've been competing with each other for high scores ever since.
So yes, at the beginning I thought it was good.
Free/Paid charts change all the time -- the apps that show up there get the most amount of downloads.
For indie games, usually any growth only comes after some celebrity or big media outlet mentions it (e.g. Angry Birds took off after some Olympic skier mentioned playing it). There didn't seem to be any such moment with Flappy Bird.