Often the main drivers to a loss of custody for a mother is the lack of support from her own parents to keep and raise her child. They often prefer to release responsibility to a stranger than face the uncertainty of how long that support might be required of them.
In an adoptees group I am part of, it was noted that adoptees would have rather been raised by maternal grandmothers with the mother nearby and somewhat involved. Not every girl that conceives a child is ready to raise it. It may even be necessary in some cases for there to be a period of time when she lacks access to her child while she tries to stabilize her own life.
In my family, though my parents were good parents, they were both also adoptees. To deny adoption as a solution might have been similar to denying the rightness of their own lives. I don’t know.
What I do know is they had this attitude that once they raised us to adulthood and we had married and started having children of our own, we were pretty much on our own financially. They might grudgingly hand us a $20 or something along that order.
They were quick to encourage my sister to give up her daughter to adoption. Adoptees noted that when the grandparents give up pressuring their child to give up that grandbaby, they quickly fall in love with the child once it exists.
Something like that might have happened with my disappointed, maternal, adoptive grandparents after I was born, having been conceived out of wedlock.
However, as a cautionary note, based solely on my own observations, within my own family’s dynamics, a paternal grandmother who dislikes the mother and gets custody of her grandson is not a good outcome . . .