I was just curious about how games get under the "popular" category on itch. Is it a certain amount of comments? Ratings? Downloads? Views? All of the above?

Usually I see some of the first games on the homepage (almost all of them are indie horror, no surprise) and they have tons of ratings and comments. 

It's a complex algorithm that's hard to guess, and also makes games move up and down all the time so everyone gets a chance.