Maybe it was a women who didn't care whether the baby lived or died
If you are right, if this woman did not care and left her baby in a park without a care in the world - and I very much doubt it is that black and white - but if she "didn't care" then something was broken in her a long time ago.
Healthy, well-adjusted, content people do not leave a baby in a park and "not care".
Women who are forced to give up their babies often compartmentalise and distance themselves from their realities, to protect themselves emotionally.
Private pain can be locked down very deeply. They might never talk about it.
Thank your lucky stars you are having such a hard time trying to puzzle over why she did this, and why it seemed to her like an acceptable decision.