Rios has been struggling with weight for a while. Guys who fight at 135 don't weigh 150 or so in the ring on a regular basis. 90% of the guys who fight at 135 weigh around 143-145 in the ring. Not 150. When you weigh what the junior welters usually weigh in the ring, then you probably should be fighting in that weight class.

Rios tried to unnaturally kill his body to make 135 for a while now. Finally his body told him no. Blame his trainer, his manager, his promoter, and him. All of them know he shouldn't have been at 135 and all of them kept rolling the dice.