To whom is all prophecy directed and why?
All prophecy is directed to the nation of Israel, because Israel will be at the core of every prophetic event. Even Revelation's judgments primarily target Israel, described as Jacob's trouble, while the whole world is involved secondarily. Israel stands on covenant ground, to receive the Redeemer, Messiah, King, and Kingdom, and through Israel God would gather the Gentiles.
In Acts 3, Peter is preaching to a Jewish crowd and says all the prophets from Samuel onward foretold these days—the crucifixion, resurrection, ascension, and coming of the Holy Spirit. Peter then calls them the children of the prophets and the children of the covenant God made with Abraham, promising that through Abraham's seed all kindreds of the earth would be blessed. Les teaches that all prophecy is directed to the nation of Israel because Israel will be at the core of all prophetic events, even the Book of Revelation. The horrible things in Revelation are primarily directed to Israel, the time of Jacob's trouble; the whole world comes along, but it is primarily Israel. Peter is on covenant ground, the same basis since Abraham: Israel was to receive the Redeemer, Messiah, King, and Kingdom, and through Israel God would gather the Gentiles. God had not cast off the Gentiles, but He would use the nation of Israel.