How do the games really recruits guards?

2 main theories i see are the following:

Their passed winners

They picked the red card when playing games with the salesman

Both these are kinda dumb because 30 guards from the 30 different games is too little. The 2nd is dumb to cause you would need some psycho people in debt to get them to agree to this, "Hey, wanna serve as a guard in murder games where you can shoot people, but hey we’ll pay you!"

I think both are dumb theories, my theory is that passed game loser families are given the opportunity to take down the people who “killed” their loved ones, i put quotes because the games could say that the players killed their loved ones, not the guards.

That theory would only apply to circle, and triangle guards

Square guards are confusing, their the higher ups but somehow the 2 that have been revealed look no older then 21

Whats your theory on the guards?