That article doesn’t say what you seem to think it says. It only talks about an increase in diagnosed cases, which can be explained away by more frequent assessments, better awareness of symptoms, the loosening of diagnostic criteria in the DSM IV, and over-diagnosis to get children with other severe developmental disorders qualified for services. There are lots of reasons we know about that autism is being diagnosed more frequently, but the best you’re going to get on your hypothesis is “we don’t know.”

https://www.scientificamerican.com/article/the-real-reasons-autism-rates-are-up-in-the-u-s/

Experts say the bulk of the increase stems from a growing awareness of autism and changes to the condition’s diagnostic criteria.

https://www.annualreviews.org/content/journals/10.1146/annurev.publhealth.28.021406.144007

Environmental risk factors may also play a role, perhaps via complex gene-environment interactions, but no specific exposures with significant population effects are known

https://www.autismspeaks.org/autism-statistics-asd

Autism prevalence is lower among white children than other racial and ethnic groups:

White – 2.4%, Black – 2.9%, Hispanic – 3.2%, Asian or Pacific Islander – 3.3%

These changes reflect an improvement in outreach, screening and de-stigmatization of autism diagnosis among minority communities.