You know that the Christians who wrote all that crap really believed that Jesus was going to come back in their lifetimes, right?
Did they, though? And does that even matter? The message they preached said "unexpectedly, like a thief in the night," and "[but stay alert]." So, it seems the real message was "whatever generation you find yourself in, understand that this will all end, so be prepared."
Perhaps hinting at the time scales, Jesus lists a number of events that must occur first, including wars and threats of war, famines, earthquakes, nations rising against nations, and the Good News that God saves people must be heard throughout the whole world. But after those struggles, the season will be one where everyone says "everything is peaceful and secure." (1 Thess 5:3) This is an awful lot that had to occur in their lifetimes.
"Sin will be rampant everywhere, and the love of many will grow cold."