Are the games going to be judged by everyone or is there select judges ranking every game? because looking at how much people entered, im pretty sure no one's going to download and vote on over 10k games

This is what it says:

"Voting will open shortly after the jam ends and is open to everyone who’s submitted a game.  Entries will be rated on the following categories: Overall, Gameplay, Graphics, Audio, Innovation and Theme Interpretation. Voting will end on TBD.

As always, we'll highlight some of our favorites games on the GitHub Blog, and the world will get to enjoy (and maybe even contribute to or learn from) your creations."

My guess is that they will play the most popular ones and/or the better rated.

Usually everyone can rate and there are a minimum number of ratings required in order for you to able to get ranked. From +- 10k entries, there are probably 'only' going to be around 2k submissions - most people have already given up and abandoned there well-intentioned projects. In a previous jam I have seen people come close to winning with just 12 ratings, and others around the same mark with over 100 ratings. Itch will work out the average but its based on that minimum number to arrive at an average score for your game.