"'Therefore I want you to know that God's salvation has been sent to the Gentiles, and they will listen!' After he said this, the Jews left, arguing vigorously among themselves." NIV translation
Why was salvation sent to Gentiles (those that were not God's people)? The simple answer is to shame Israel by letting them see that the gift they had rejected (Jesus) would be gladly accepted by others. This fact brought controversy to the Jews as they could not see the that it was God's plan all along.
"For two whole years Paul stayed there in his own rented house and welcomed all who came to see him. Boldly and without hindrance he preached the kingdom of God and taught about the Lord Jesus Christ." NIV translation
In this final passage of the book of Acts, we see that God is faithful and will deliver His people for His purpose. We might ask why God allowed Paul to go through all that he did and we see the reason contained in this passage. He was able to spread the gospel of Jesus Christ in the heart of the Roman Empire "without hindrance".