Except that is not true. We know from texts that if anything old "geniuses" were not autistic, but they were on the bipolar spectrum, or more generally on the affect spectrum ( mood disturbance ). Winston Churchill for example is famously bipolar. Many texts refer to feeling an overbearing sudden sadness, as in bipolar depression spectrum.

Autism and schizophrenia are so horrible because they are not on the affect spectrum. So in a historic view autism is indeed a new and a modern madness.

I would recommend the book "The Master and His Emissary" by Iain McGilchrist.