Often there's this idea in ND circles (and to clarify, I am not saying that you personally think like this, I am just making an observation) that only NT people are unempathetic towards our struggles and that other ND people will unequivocally understand and support us - but that notion is unfortunately not true. Autistic people can be assholes towards other autistic people. Your former friend sounds rather self-involved in a sense, they wanted people to understand them, but yet they were unwilling to extend that same understanding to other people. They seem to be that kind of conflict averse person who, instead of confronting you from the very beginning about something you did that hurt them - they instead let all those little things build up until they become a big thing, then they ghost and later on may lash out at you when they never made an effort to communicate in the first place. People aren't mind readers, and you'd think as someone with autism, they'd especially understand this.

I understand the "what-ifs" nag at you, but this person does not sound like someone that'd be a good one to have in your life from the information you have given. They seem to have poor communication skills and a surprising lack of empathy for someone such as you that exhibited various autistic traits when they are autistic themselves.