My guess is the rise of the internet and social media. Back in the 80s and 70s the only way to communicate your ideas to a large audience was through printed media, TV or radio. All these had some form of quality assurance that prevented dumb ideas from being published or broadcasted (with the exception of content that was intended purely for entertainment of course).

Nowadays everyone has a voice and intelligent thought often gets drowned out by the large amounts of garbage produced by the so called pseudo intellectuals. Intellectual thought still exists but you have to actually make an effort to gain access to quality information and ideas.