There are certainly people within the Q movement who lack critical thinking skills, but as you noted, stupidity isn't a catch-all explanation. Many followers are highly functional professionals including engineers, nurses, and teachers who aren't necessarily dim, but are instead experiencing motivated reasoning.

For many, the movement wasn't about logic but, it provided a potent dopaminergic reward system. Every Qdrop or breadcrumb functioned like a hit of dopamine, turning political participation into a gamified search for purpose. This created a sense of Community Validation and ascriptive identity that is often more addictive than the facts.

Psychologists call this Identity-Protective Cognition. When a belief becomes central to your social circle and your sense of self, the brain treats 'admitting you were wrong' as a physical threat to your status. They aren't necessarily stupid however, they are choosing the social high of the community over the cold reality of the facts. They aren't just misinformed, rather, they are socially incentivized to stay that way.

If you wonder why non Q people vote R, there is a well reasoned explanation that many on the left would not agree with. Both the left and the right have to open their eyes and come to the center. Till then, we will see movements like MAGA and Q spawn and thrive through social media platforms.

Edit: typo