Dustin and Max weren't at their peak yet when Conor fought them. Those fights are sandwiched between a win over Diego Brandao, which is around the level those other two where seen at around this time.
Conor is a product timing, luck, and preferential treatment from the company. He was able to avoid wrestlers during his ascent, and when he was finally forced to face one, he chose the one without a full camp (Chad Mendes), when he had the choice to fight a fight ready Frankie Edgar (who was also ranked higher than Chad at this point).
“[When Jose Aldo was forced out of UFC 189] he knew Mendes wasn’t in a camp, that he was filming a hunting show and he hadn’t trained in a long time. He knows that Frankie trains all year round and it would’ve been perfect timing. Mendes had just lost the fight before to Aldo. That week, Frankie was ranked ahead of Chad too and they switched it fast after Chad got the fight…Frankie was ranked ahead of him, he had more wins than him. Chad had just lost within two fights prior to the title fight.”
Source
There is also his loss Diaz and his poor performance in the rematch (that many thought he lost as well). He never defended a title or showed an all around MMA game. He was a very exciting and high level striker to watch at one point, the rest is all smoke and mirrors.