Many people reject God's salvation, here they blaspheme the truth when told the truth and the apostles tell them they consider themselves unworthy of eternal life, but those who did receive Christ were born of God as they had been prior appointed by the Father to eternal life and so believed. Jesus taught that all those the Father gives to Him will come to Him. And those who come to Him he will never cast away.
John 6:37
Acts 13:45-48New King James Version (NKJV)
45 But when the Jews saw the multitudes, they were filled with envy; and contradicting and blaspheming, they opposed the things spoken by Paul. 46 Then Paul and Barnabas grew bold and said, “It was necessary that the word of God should be spoken to you first; but since you reject it, and judge yourselves unworthy of everlasting life, behold, we turn to the Gentiles. 47 For so the Lord has commanded us:
‘I have set you as a light to the Gentiles,
That you should be for salvation to the ends of the earth.’”
48 Now when the Gentiles heard this, they were glad and glorified the word of the Lord. And as many as had been appointed to eternal life believed.
What happened in Acts 13 is what is written in John 1 and John 3, they were not born of their will, they were born of God.
John 1
10 He was in the world, and the world was made through Him, and the world did not know Him.
11 He came to His own, and His own did not receive Him.
12 But as many as received Him, to them He gave the right to become children of God, to those who believe in His name:
13 who were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.
John 3
18 “He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God. 19 And this is the condemnation, that the light has come into the world, and men loved darkness rather than light, because their deeds were evil. 20 For everyone practicing evil hates the light and does not come to the light, lest his deeds should be exposed. 21 But he who does the truth comes to the light, that his deeds may be clearly seen, that they have been done in God.”
1 John 5
Whoever believes that Jesus is the Christ is born of God, and everyone who loves Him who begot also loves him who is begotten of Him.
2 By this we know that we love the children of God, when we love God and keep His commandments.
3 For this is the love of God, that we keep His commandments. And His commandments are not burdensome.
4 For whatever is born of God overcomes the world. And this is the victory that has overcome the world—our faith.
5 Who is he who overcomes the world, but he who believes that Jesus is the Son of God?