TotalBiscuit. I think I found out through his Steam Curator page, which I follow.
How Did You First Hear About Chrono?
Karhoum
#63
Totalbiscuit as well, been visiting the site on and off since then, now I visit daily since the introduction of coins 
crazyLoudmouth
#66
I discovered this awesome site by the deal you made of Lastfight. Indeed, this game come from a French comic called Lastman, and it kick asses, it’s an awesome comic. By the way, they even made a animated serie of Lastman that will come in English in some time 
I advise you all to watch it since it’s so great!
Mrteatime
#67
I heard about it through Total Biscuit’s promotion of the site.I liked the idea so I checked it. And i do not regret it.
Sophron
#68
Like many other people here it was TotalBiscuit’s promotion of the site and I kept an eye on it from time to time. I believe his first video was about a year or so ago. It wasn’t until his second video about the coins I finally decided to join up.
SirFloof
#69
I first heard about ChronoGG from Caddicarus, but I quickly forgot about it. I only decided to check it out after TotalBiscuit praised it in one of his videos.
Truly
#71
I think I register after a GDQ thing, I’m not sure. But I came back when TB mentioned it I think… God my memory is bad.
Enki
#72
Chronicon Discussion Board, a topic talking about ZiggyD’s video featuring Chronicon and Chrono.gg promo on the game.
Ctouw
#73
I was reading messages on SteamGifts Discord server and someody simply wrote “Chrono.gg” to remind others to get their coins. He did this everyday so eventually I checked on google what Chrono.gg was. And here I am ! 
ViralDragonRider
#75
I subscribe to nerdcubed on patron and he is thinking of setting up a deal with Chrono so he let his patron followers have a say. And i liked the idea of a different game on sale each day so now i’m here
Gnuffi
#78
i honestly can’t remember, you expect me to be able to remember that far back, 
i can barely recall what pants i had for breakfast or which leg i put in my oatmeal first this morning 
possibly Cynical Tophat Biscuit British Halibut McBain, can’t say for sure 
wait, -why are there footstep shaped oatmeal splodges on my floor?!
nebula7
#79
It’s really sad what happens to gnomes when they get old, can’t even tell the difference between pants and oatmeal. Sad!
Halcypher
#80
Total Biscuit
Seems that having a big name promote one’s site gets one users… I’m flabbergasted
Edit: although to be fair, that’s not entirely accurate, the interest is piqued, but one keeps the users by being a good site with a good community. Yay, well done Chrono!