The pope of the Shining Cathedral of Radiance wasn't above in status to the Holy King of Aralos, but their standing in the kingdom of Aralos was pretty much the same.
After all, one was the spiritual leader of the most revered religion in Aralos, and the other was its secular ruler.
Moreover, they were equals in magical prowess, both being grandmasters wizards on the cusp of ascending to the lord-ranked wizard stage.
To give an idea of their strength, this entire world didn't boast a single lord-rank wizard. There were only ten grandmasters of such caliber in this world.
Considering this, how could the Holy King demand the Pope to kneel for his decree?
To be honest, no smart ruler would do something that might result in them disappointing, offending, or losing a grandmaster wizard of such magnitude!