Nah, that is not really true. There has been a significant bump due to covid, but before covid IQ test results have shown constant improvements.
That said, I don’t think IQ and political idiocy are that strongly correlated. I’ve met a lot of highly trained people, who would doubtlessly get great IQ test results, who are politically extremely gullible.
That also said, IQ tests are a quite flawed way to assess intelligence.
My personal believe is: This is not about people getting dumber, but about propagandists getting better. I also think that unsteadiness is a way better catalysator for fascism than low intelligence.
Check them out. Some are great (Cranberries and Blur for example). I also guess you’ll know more than you think.