You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
alternatehistory.com
Basically this question. Many of the most well known Emperors especially during and after the Crisis of the 3rd Century were of Illyrian descent eg (Aurelian,Diocletian,Gothicus Constantine etc). Was it because Illyria was heavily colonized.