I think there is a lot more to this case than what is in the article. Why was the baby fostered in the first place? There must have been significant concerns at how at risk it was and possibly they didn’t feel it was safe for the baby if mum didn’t have 24/7 support which perhaps couldn’t be provided. The autism part could be a bit of a red flag, plenty of people without autism self harm and don’t get adequate support. Plenty of autistic people make excellent parents.
Ultimately, better care for any vulnerable person should be given and nobody should be told in an email their baby is going to be adopted, it’s definitely the kind of thing that needs to have been properly discussed face to face.