Who was the Old Testament directed to?
The Old Testament was directed almost exclusively to the nation of Israel, God's covenant people. Scripture shows it was not quite exclusively, but almost entirely focused on Israel, with only a few exceptions noted. This was God dealing with His covenant people before a parting of ways in His program.
Les explains that everything up to that point in the Acts account was God dealing with His covenant people. He notes that everything up through the Old Testament, as shown in a previous series of programs, was directed not quite exclusively but almost entirely to the nation of Israel. There were some exceptions, but now there is a parting of the ways in God's program for the human race, as He begins to deviate from the whole concept of Jew only.