Why did the twelve apostles stay in Jerusalem even when they were under pressure?
The twelve apostles remained in Jerusalem under pressure because their King was going to return imminently to Jerusalem, specifically the Mount of Olives. They also knew Israel's national repentance and the fulfillment of prophecy had to come first; only afterward could they take the gospel of Abraham's God to the Gentile world.
Les teaches that these twelve men do not leave Jerusalem, not even under pressure, because Jerusalem and the Mount of Olives are where their King was going to imminently return. God was still dealing with the nation of Israel: if they would repent of their national sins and believe who Jesus was, God would have brought in the tribulation, it could have run its course, Christ could have returned, and Israel could have had the kingdom. Peter and the eleven knew that when this was fulfilled, they could then take the gospel of their God of Abraham to the Gentile world, but not until then. Les also points to Zechariah 8:20-23, where many people and strong nations come to seek the Lord of hosts in Jerusalem and to pray before the Lord, confirming Jerusalem's central place in this prophetic program.