The problem is that if Jesus’ (and Paul's) end of the world prophecies are taken at face value, it is clear that Jesus was expecting the world to end during his generation/lifetime.
Why was Jesus expecting the world to end during his generation?
According Bart D. Ehrman in his book: “Jesus – Apocalyptic Prophet of the New Millennium”
http://www.preteristarchive.com/Books/pdf/1999_ehrman_jesus-apocalyptic-prophet.pdf:
“Apocalypticism” was the order of the day at the time Jesus is said to have existed because of the history of the Promised Land. Jews in Palestine had been under direct foreign domination for most of the eight centuries prior to the time it is said Jesus was born. The Promised Land was conquered in succession by the Assyrians, the Babylonians, the Persians, the Greeks, the Syrians, and the Romans. Jews resented the idea that they were answerable to a foreign power. They were, after all, the chosen people of the one true God of Israel, the God who had agreed to protect and defend them in exchange for their devotion. This was the land that he had promised them, and for many of them it must have been more than a little distressing, both politically and religiously, to know that ultimately someone else was in charge.
There was the belief that there would be an imminent intervention of God on behalf of his people, an intervention to be modeled on earlier acts of salvation as recorded in the Hebrew Scriptures. Quite soon, God would reassert himself and bring this world back to himself, destroying the forces of evil and establishing his people as rulers over the earth. When this new Kingdom came, God would fulfil his promises to his people. This point of view, commonly called “apocalypticism”, was an ideology that tried to make sense of the oppression of the people of God. Jewish apocalyptic thought was evident in a number of writings both in the Hebrew Bible (e.g. book of Daniel) and from other sources.
Some of the earliest traditions about Jesus portray him as a Jewish apocalypticist who responded to the political and social crises of his day, including the domination of his nation by a foreign power, by proclaiming that his generation was living at the end of the age, that God would soon intervene on behalf of his people, sending a cosmic judge from heaven, the Son of Man who would destroy the forces of evil and set up God’s Kingdom. In preparation for his coming, the people of Israel needed to turn to God, trusting him as a kindly parent and loving one another as his special children. Those who refused to accept this message would be liable to the judgment of God, soon to arrive with the coming of the Son of Man.