Is explained in detail in this wonderful blog post over at The Imaginative Conservative: Russell Kirk Would Have Been a Great Headmaster. Well worth a read. Kirk had a good deal of insight about the intellectual collapse of the humanities in the last half of the 20th century, having walked away from his teaching job at a college he would later refer to as "Behemoth U."
Of course, the problems with the modern American university have their origin further back than the middle of the 20th century, but it was after World War II that the mass rot set in. The combination of the democratization of university education with the ideological radicalization of the faculty in the 1960's appears to have been the catalyst for the problems we find ourselves in today. The "higher education bubble" that many write about today is simply the latest symptom of the disease that Kirk was so apt to diagnose back in the day.