Maybe he has his reasons, maybe he doesn't need any...
Rom 9:13 As it is written, “
Jacob I loved, but Esau I hated.”
Rom 9:14 What shall we say then?
Is there injustice on God's part? By no means!
Rom 9:15 For he says to Moses, “
I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.”
Rom 9:16 So then it depends not on human will or exertion, but
on God, who has mercy.
Rom 9:17 For the Scripture says to Pharaoh, “
For this very purpose I have raised you up, that I might show my power in you, and that my name might be proclaimed in all the earth.”
Rom 9:18
So then he has mercy on whomever he wills, and he hardens whomever he wills.
Rom 9:19 You will say to me then, “
Why does he still find fault? For who can resist his will?”
Rom 9:20
But who are you, O man, to answer back to God? Will what is molded say to its molder, “Why have you made me like this?”
Rom 9:21
Has the potter no right over the clay, to make out of the same lump one vessel for honorable use and another for dishonorable use?
Rom 9:22
What if God, desiring to show his wrath and to make known his power, has endured with much patience
vessels of wrath prepared for destruction,
Rom 9:23
in order to make known the riches of his glory for vessels of mercy, which he has prepared beforehand for glory—
Rom 9:24 even us whom he has called, not from the Jews only but also from the Gentiles? (ESV)
I agree with John Piper that:
"God is free to have mercy on whom he’ll have mercy. He is free to show mercy and grace to whomever he wills. Nobody deserves it, and God is not unjust to give it freely to whomever he will, and not to another.
...
Paul’s overall point in this section is that God is just in having mercy on whom he will (
Romans 9:14). He does no one — no human being ever anywhere — any wrong. He always upholds the infinite value of what is infinitely valuable — that is, his righteousness. He upholds his glory.
In his absolute, glorious freedom — “I’ll have mercy on whom I have mercy; I’ll be gracious to whom I’ll be gracious” — he makes known the riches of his glory for the vessels of mercy. That’s verse 23, and that’s the ultimate goal of the universe. Those vessels of mercy are prepared beforehand by God for glory.
But in this very moment, the vessels of mercy (I’m talking now to our listeners) are everyone and anyone who calls on the name of the Lord."
https://www.desiringgod.org/interviews/why-does-god-choose-some-and-not-others
