Alex's suggestion for what could be done with Pearl's father's corpse was simple and even quite beneficial for Alex himself and the others. And yet at the same time, it was as though he was trying to take advantage of the Azure Dragon's death.
The two conflicting feelings made it hard for Alex to even suggest this option to Pearl, to begin with, but after hearing that he did not wish to bury his father, he decided to ask Pearl.
Pearl gave a lot of thought to what Alex proposed, not getting angry at him for suggesting what he did. Instead, he decided calm-headedly that maybe that would be the proper thing to do.
In a way, if he were to do this, his father could forever be close to him when he needed him.
With Pearl deciding to do it, Alex gained the confidence to do what had been decided.
So, he began his preparation.
He was now going to feed the Immortal body of the Azure Dragon to the World Tree.