It’s likely common cause, rather than cause==>effect.

Something happens in the developing brain that is either a malfunction, or a wildcard switch. Either way it leads to a lot of ‘minor’ changes to the brain. It’s part of the reason they half gave up exactly defining autism. It’s a cluster of small changes that come as a group. Some useful, some negative.

The joke about the proportions of geniuses and the insane being lefties has some grounding in reality.