I was posting on a league of legends forum during my second attempt to get into that game and there was some dude who was full of shit bragging about how playing osu is how he got some quad kill or something because of reflexes.
I didn't care about the guy's actual post, but he included a video of his osu gameplay, and I realized it was a rhythm game, and I had loved rhythm games from my childhood because I used to have DDR and a dance mat. However, most rhythm games I'd tried to play were too complicated for me to learn and get into. Even now I still can't play Mania.
And I was like dude whatever I need stuff to play, and this game looks really interesting. So I downloaded the game, played casually Mouse only for about 3 months before getting a tablet and playing hardcore for the better part of 6 months, before I peaked out and stopped playing seriously.
What's more is that attempt to get into league was only like 1 week long, and I wouldn't have found the game otherwise. How different my life would have been if that one dude hadn't posted that one troll topic about osu, on that one specific week I was playing league and posting on those forums. Most of my online friends are people I've met through this community, so it's safe to say this game has changed my life.