He didn't face the highest level of competition. In fact, his competition level was pretty weak. Very consistent and well schooled, of course. Didn't skip training yadayada. Had the tools over everyone he fought.
Technique!!! Well schooled and well disciplined fighter who was also able to be dominant years after his prime because the division was weak. How many adult male 105lber's are there in the world? The ones that are athletic usually become jockies. Well paid, safer and much longer career than a pro boxer.
He lived very clean and took the sport very seriously. He was a gym rat as all Nacho Beristain pupils had to. He’s also very skilled. Add all of this to a largely weak level of competition and then only fighting very rarely the last few years and it all makes sense.
He was clearly a few years past his best by the time of the Alvarez fights. He was lucky to escape with a draw in the first fight, and had to dig deep to win the second. His wins after that were superficially good but carefully selected; Sor Vorapin was more faded than Lopez (despite being a lot younger), and Grigsby and Petelo had built almost their entire rep on beating Sor Vorapin. Technically sound fighters like Lopez can often draw their careers out over a longer period than fighters relying on overwhelming atttributes.