Autism presents very differently from person to person. Its tough to look at someone and say “oh, that’s autism.” It is significantly more challenging to define and, consequently, much more difficult to pigeonhole. Because of that, many people assume that autistics have classic “insanity.” For the record, they are not the same thing.
Normally I would use reductio ad absurdum to show that the concept of insanity is outdated and based on a mental health model better left in the 1800s. I do not, however, have time to cover 100+ years of mental health so I’m going to say simply that the new crazy is much more well defined than the old crazy. The DSM-IV breaks out a number of conditions that were once lumped together. Autistic disorder is just one of those with an expanded definition.