I expect B8 is the major factor. Before social media, if you had a bad idea and two of your five close friends told you they didn’t think it was a good idea, you’d drop it. Now five random ‘friends’ will tell you how insightful you are and how blind everyone else is. You’ve publicly stated your belief in the idea and got social proof. That makes it that much harder to drop.
People individually don’t have more bad ideas than before, but there is much more selection pressure in favor of them.