Only about 10% of autistic people are savants. And only about 50% of savants are autistic.
And infinity symbol, autistic people have /less/ dense white matter and less instances neurotransmitters like dopamine, oxytocin, serotonin. There are also disruptions in the medial prefrontal cortex, superior temporal sulcus, fusiform face area, and the amygdal. These areas affect "theory of mind" -- our ability to understand that people have different thoughts, desires, motivations, etc. than our own.
Theory of Mind is the "big" hypothesis with Autism right now. Essentially, autistic people do not understand how people expect them to act. They can't determine the intentions of others and can't probably assess how their behaviors effect others.
(Fun fact: One of the leading researcher's in this field is Sacha Baron-Cohen's cousin, Simon Baron-Cohen).