[themagician]

It is primarily driven by the expansion of the diagnosis itself. DSM-3 Autism (1980) is quite different from DSM-5 Autism (today). We use the same word to describe two different things. Today's autism includes things that used to have totally different names. It also "allows" for a diagnosis much later in life. Autism used to be something very specific and discreet. From another perspective, the rate may not be soaring. That is, many more people in the 1980s and 1990s would be autistic by today's new standard.

[seba_dos1]

That's just because today we understand it better. What "autism" used to mean is a certain set of comorbidities that appear to be caused by autism combined with external factors, but that's just because we didn't know how things were connecting to each other back then (and there appears to still be a lot to learn about that).