Another great point Anthony. How about the thief who died with Jesus. What was the cause of him being saved.
God's grace.
...and I will have mercy on whom I will, and I will be merciful to whom it shall please me.
[Exodus 33:19]
Also both criminals on the cross mocked Christ with the jews
38 Then were crucified with him two thieves: one on the right hand, and one on the left.
39 And they that passed by, blasphemed him, wagging their heads,
40 And saying: Vah, thou that destroyest the temple of God, and in three days dost rebuild it: save thy own self: if thou be the Son of God, come down from the cross.
41 In like manner also the chief priests, with the scribes and ancients, mocking, said:
42 He saved others; himself he cannot save. If he be the king of Israel, let him now come down from the cross, and we will believe him.
43 He trusted in God; let him now deliver him if he will have him; for he said: I am the Son of God.
44
And the selfsame thing the thieves also, that were crucified with him, reproached him with.One of the thieves would repent and be saved, the other would not and be damned. And why? Because God will have mercy on whom ever He wills. No one is owed salvation, and grace is a gift (hence the name grace). Having mercy on one thief was a miracle and increases the glory of God through His mercy. Allowing the other thief to die in his sins increases the glory of God by His justice, as sinners get what they deserve.
Hence yet another reason I agree with St Augustine where he writes against Julian, "let it not be said that God will allow any of His elect before receiving the sacrament of the mediator", because God is always in control, Divine providence will always provide as God's will be done, and why one dies a catechumen before baptism (who may have seemed like a good/kind person by humans judgment) while another who is terrible may be saved. Because God allowed it to happen, there is no need or place to question why God saves one but not another.
O the depth of the riches of the wisdom and of the knowledge of God! How incomprehensible are his judgments, and how unsearchable his ways!
[Romans 11:33]
* Note that the thief died under the law old before the promulgation of the Gospel and did not need to be baptized, though we see in the Gospels that when Christ rose from the died some of Saints also rose with Him, so it's possible the old testament Saints were baptized during the 40 days before the Ascension
And Jesus again crying with a loud voice, yielded up the ghost.
51 And behold the veil of the temple was rent in two from the top even to the bottom, and the earth quaked, and the rocks were rent.
52
And the graves were opened: and many bodies of the saints that had slept arose,
53 And coming out of the tombs after his resurrection, came into the holy city, and appeared to many.