Assuming Autism has increased recently (and the term is 20th century, and was not considered a problem until the late 20th century), many things correlate with the rise of autism:
Lower infant and maternal mortality
Increased age of parents
Antibiotics
Automobiles
Electrical appliances in the home
Radio, television and the internet
Professional sports
Israeli independence
A diet high in calories (previously calorie deprivation was crisis – people used to be starving much of the time
People often grasp at something seeking an answer. You see it in those trying to relate climate change to policies they disapprove of. Sometimes this gets controversial (as in the correlation between rising abortion rates and falling crime rates). Often it gets ridiculous (the anti-vaccine people verge on this).