The apostle quotes David in a psalm about the people who were speaking evil of him. Let them be bent over is to be rendered powerless. I would imagine that the king was talking about an uprising in leadership. Its important to see that the king curses those who are unfaithful. This unfaithfulness is to apostatize from the faith.

We must understand that God through the prophets spoke His warnings to them all day long. But not all Israel is Israel. God always preserved a remnant within Israel. When David spoke these curses it was to those who were traders in his own government. Possibly led by Absalom.

God spoke through the prophets calling His people evil. But at the same time the prophets called them righteous. This is puzzling because in the ot a blessed person is never addressed as wicked. What we need to see here was that the prophets were like the modern day evangelist. They spoke to the nation as a whole. So they were addressing three kinds of people. The wicked, the self righteous and the elect. You never see an Israelite curse His own people. But he cursed the wicked. And so there were wicked and self righteous people in Israel.

The apostle here is speaking of the nation of Israel. God did not reject His remnant people. And this is what the apostle talks about in the same address in Romans. But God preserved His elect even when they suffered in exile. So the apostle is not saying that God was waiting for Israel to turn to Him but through their rejection the gospel went out to all the world.