My pet theory on autism is the Back to Sleep campaign that began in the 90s. (1) Babies don’t like back sleeping. It disrupts their sleep. Sleep is important in brain development. Constantly disrupted sleep means a higher percentage of brain development issues.
I can back up my pet theory with studies. Bottom line is, stomach sleeping with good air circulation (2) reduces SIDS at similar rates to back sleeping without the side effect of autism.
1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4978628/ 2: https://jamanetwork.com/journals/jamapediatrics/fullarticle/...