No we don't C'est but I do know from my own experience that being seen to have money or an education can be used by SSD as an excuse not to help, we get no respite or provision whatsoever and our alst carers assessment used my relevant - to - disability post grad as the reason no help was needed. It was and is, badly. I had a breakdown a few years ago and GP begged for help but none was forthcoming. I have given up on SSD now in entirety.
I cannot speak for this family, but I did work in a related field of family support and I know that the families we had who were perhaps of a higher social economic status or community standing often found it harder to ask for help as they felt they would be letting people down, risking their standing or even dismissed as not being in need due to finances or the nice house must be OK factor. Yes a night Nanny is useful if needed or whatever but even that's not simple- ds1's violence for example is so bad that we were told that if any harm came to an employee we hired (we were better off then) we would be liable as we knew the risks.
I can;t condone what she did, I don't know her individual circs either, but I do know that money can only buy so much. I imagine you'd probably be better off being poorer but with a close family (geographically and emotionally), for example (as someone who knows what moving away from that family added to stress). I also know there is a complete lack of services geared for those of us with multiple disabled kids. personally i think we actually scare the services away as we are not so much £ as ££££. It would take the entire local respite centre to give us a single night off; or they can help three other families with the one needy child.
I also know that some people are simply weaker and break more easily. I am strong, I presume you are too C'est, but DH had a lot of MH issues initially coming to terms with the ASD. I have a lot of theories about that (his parents saw SN as the end of the world, he was never exposed to disability in his life before the boys whereas I went to one of the first schools with a mixed SN / MS intake).
I cannot justify what your ex did and I have no wish to, it is never OK to harm any child, the disability is irrelevant to that really. But when such a tragedy as this happens we can seek to understand, and learn from it to stop it happening again. That has to count for something. Not to you- that would be a ridiculous ask- but to society as a whole.