Well, there's something about God that my my mind cannot fathom. Imagine God saying this

And he said, "I will make all my goodness pass before you and will proclaim before you my name 'The LORD.' And I will be gracious to whom I will be gracious, and will show mercy on whom I will show mercy. (Exodus 33:19, ESV). He is God and He does what pleases him. It's hard to understand such things but He's doing all for His glory.

Maybe the most stubborn child is going to be used by God massively. Who knows? Paul said he was the greatest of all sinners. But see how God changed him instantly for his service.