People have an amazing capacity to tolerate things, especially in a group setting with someone in control when it builds over time and they have witnessed others accept this behavior.
I don't know how it got to this point but assume this coach loses it and screams at a player calling him a sissy one day in practice for not taking a charge or screening hard enough. Probably not right but not that big of a deal. Most players would probably accept it because the coach controls their scholarship. As a result no one says anything. Next it is a fairy. Then a fagg*t, etc. etc. Still the players don't do anything and they are being verbally abused on a daily basis. Then the physical stuff happens slowly but progresses to the point of the video. Now assume a new player enters the program when the coach is fully out of control. He thinks it is insane but not one player speaks up. The kid wants his scholarship, no one else is complaining so he he wonders if it is just him and says nothing. Next thing you know that new kid starts to think this is normal or somehow acceptable.
I am not saying this is how it happened. I am simply pointing out that these players may not be all that different from you or me. They were likely conditioned over time to accept this behavior.
Lets hope now that this coach has been fired he also gets sued and loses some serious money to the players he abused. Those kids had one 5 year window to play college sports and he stole it from them with his abusive behavior that clearly appears to be assault, battery and intentional infliction of emotional distress.