Rashek was 1,500 years ago and did use the stormin Well of Ascension to become the LR so he would be more of an outlier than the rule so it would still be abnormal for a commoner to become the Governor
And as Aspiring said Rashek saved humanity from destruction continuously for 1,000 years with all his programs and hiding the Atium. That line in TFE was supposed to sound egotistical then and than make sense in HoA when you realize that he did do a lot for humanity