So to answer some of the Qs about attachment etc, ill share what I have seen in previous roles with childrens services. A lady who was a teacher asked something around this.
A typical situation could look like this:
Mum experiences adversity in her life for any number of reasons, this can impact on baby brain development in utero (epigenetics). Baby is born and mum (for a host of reasons) struggles or cant form secure attachment to baby, baby does not receive responsive attuned care. Mum cant co-regulate babies distress. This could look like baby being put in front of TV+++, not being responded to when crying, spending lots if time indoors, lack of real world experiences, late weaning, lack of exposure to varied taste and texture. Developmental milestone delay. Baby starts nursery and is way overstimulated due to its world being so small previously, lack of attachement observed (reduced eye contact, sensory seeking etc) concerns noted.
Child starts school and these increase, mum also notices difficuties in managing childs behaviour, mum herself experiences maladaptive coping, increased high expressed emotion, poor communication. Child cannot regulate and spends lots +++ of time on screens (often viewed as 'the only thing that works') and dysregulates when its taken away, has very limited diet and sensory issues, which all compund mums view its ND.
This then manifests as home and school both notice issues and child can go down the asd assessment route. Attachment disruption can present with many similar symptoms.
Of course in this there will be children who have ASD regardless of experience or environment, but I have seen the above play out again and again and again.
This is based on families i have worked with, and only work with due to them having a range of other concerns, so I dont see the 'average' family, I am not suggesting parents are to 'blame' for ND AT ALL, but its important to consider the overlap with differential diagnosis.