It's both.
It's all of this. Especially the first and second points.
Back when research into autism was first being done, one of the predominant theories for its cause was something called "
refrigerator mothers" a.k.a. neglectful mothers who didn't show their children any warmth, or affection. Turns out while that's not true for autism, it is true for something called Reactive Attachment Disorder, or RAD for short. The symptoms of that condition overlap a ton with the ones of autism such as poor eye contact, lack of emotion, or empathy, strong attachments to objects, etc.
With the rise of technology, and its plague on society, the fact most of natural selection has gone out the window, and that treating our environment like a shithole is finally coming back to bite us in the ass, more, and more people are raising children who have a higher chance to be disabled either genetically, via poor parenting, by the environment itself in vitro, and horrifyingly, sometimes all of the above.
The rates also gone up because there's been more diagnoses of it in women now like
@Android raptor said.