Ryan Thomas, who had been alienated from his father in his childhood, explains some basics here:
https://www.youtube.com/watch?v=IHK0qKCjNBoHe describes 2 types of children, the oblivious child and the hostage child. His theme was to keep up your repeated contact, never give up, no matter what. Because if you do stop then the alienating claims are instantly confirmed. Perhaps in future months or years the child, when older, may finally be able to listen or be mature enough to put the pieces together and allow more contact or reconnect.
This concept isn't new to us and I didn't hear him explain
why a parent would be so determined to relentlessly alienate, but overall his theme was clear, encouraging and presented very well.