Paathurnax is getting a lot of racism here.
IRL if a new force (in this case mankind, led By Paathurnax) beats the lands original owners (the dragon cult) then the new group would take over and the leader would reign. this has happened hundreds of times across the earth in medival times, so why wouldent it happen here? Not to mention the fact that the rebellion would have failed without him.
In a way, he DESERVES to rule mankind based on his past good deeds, even now though all he seeks now is leadership over the dragons.