Leftist agenda was the default position of philosophers in the USA. On the other extreme you had Heidegger and that kind of approach did not seem right to Middle Americans who fought the Nazis. Philosophers were simply not very smart as the affair with the NY Physics professor that got a essay of complete nonsense but with the right jargon published in the most prestigious philosophy journal. It took a long time for people with real talent to start noticing the problems with academic philosophy. The job of philosophers is to learn an obtuse jargon which inspires awe. People think, "Gee golly, you must really smart to understand that stuff!"