The TL;DR is simply that some of his childhood friends from boxing, or their families, were involved in the drug trade and met violent and untimely deaths. He probably could have gone down that path and maybe even did briefly (he stole some money from Kavanagh early in his fighting career) but eventually got away and found an outlet in MMA. It's all factual stuff and easily verifiable.
One thing i'd add is that for someone who has seen all this stuff up close, lost people he knows to the drug gangs, his whole El Chapo schtick was very silly and inappropriate. Joking or not that dude is scum and nobody should glorify him or make light of the stuff he has done.