It's because of his mindset that becomes stubborn. Others thought that his stubbornness will kill them all due to his strength so they sent him back but I think there's more to it.
Soo is he gonna kill them or not
But look at what they did, power went to their heads after he was sent back. Making them worse the king they defeated
the words were literally said "he has become too powerful to control" in the fight over killing kids of the enemy.
It's because of his mindset that becomes stubborn. Others thought that his stubbornness will kill them all due to his strength so they sent him back but I think there's more to it.