Almost every one of the possible explanations (for rising stupidity, and for rising perception of stupidity if it isn't real), looked plausible to me. But that

Almost every one of the possible explanations (for rising stupidity, and for rising perception of stupidity if it isn't real), looked plausible to me. But that probably just means that "stupid" isn't a word with a precise enough definition, and so for each of the possible ways to define it, one (or more) of the various answers applies. But, in general, it seems not unrelated to the phenomenon in which weird things are much more commonly encountered (due to the ability to see/hear/read about things happening to anyone, anywhere, anytime). Weird (and perhaps also stupid) floats to the top of the list of things to be perceived, and there is now an industry (or several) to bring them to us all the time.