Why did God turn to the Gentiles?
God turned to the Gentiles because Israel rejected everything of the covenant promises. At that point God said He would take a different tack, and so He went to the Gentiles. This marked a fork in the road, with the twelve's Gospel of the Kingdom distinct from Paul's message.
Les explains that once Paul begins his ministry, he never uses the term 'Gospel of the Kingdom' because that term was associated with the twelve. Just as the twelve could not use the term 'Body of Christ,' Paul could not use 'Gospel of the Kingdom,' because they are forked in the road. God came to the point when Israel rejected everything of the covenant promises, and He said, 'Now I'll take a different tack.' So He went to the Gentiles. Paul lays this out in these verses.