When you have a big strong guy come into the gym, and he likes to fight and catches on to punching, it is tempting to let it go at that. Just tell him that all he needs to do is get out there, hit the other guy and go home. And you can perpetuate that myth through the early part of a guy's career if you have the pull that Angulo's management had. Then he moves up and gets into some fights and you can tell him that if he works out hard enough, gets into good enough shape and fights hard enough, he'll be ok.
But then you move up again, and you fight top guys. If you don't know how to avoid getting hit, if all you have is heart and a willingness to fight on, you can get hurt. They can take it all out of you real quick. Your career expectancy is limited when every fight is a hard fight.
It is easy, real easy, to teach a guy how to throw punches. Anybody reading this, in an hour, I can teach you to punch well enough to make you think you missed your calling. What is hard to teach is how to box, how to not get hit, how to move and how to think. No way you can teach a guy that up front, but you have to teach him enough to know how to learn, and you have to constantly guide him.
Angulo got walked along at the start, but he was never taught what he needed to know.