Yes it is definitely stupidity. And that's simply because it is ignoring reality at the most basic level of reason & understanding.
Perhaps that's why such people choose to adhere to conspiracies that do not affect them directly. For example; a 'Flat Earther' knows that he will never actually fall off the edge of the earth. So he can continue to tout that there is a definitive edge of this 'huge disc' without any fear that he could die that way. But if there was an off-the-wall theory or conspiracy that would clearly endanger them in a direct way, it wouldn't be one that he would choose to challenge.
The only thing that is 'evolving' here is the stubborn desire to oppose all authority. We live in a society today where people will disagree simply to disagree, because they do not wish to conform to anything. It's their definition of being 'their own person'. How sad.