We should have known this better about childhood attachment

We need to distinguish between attachment relationship, and attachment style.
Attachment relationships are the dependency relationships a child develops toward a caregiving adult. Primary attachment relationships reflect the child's experience of care and protection from that adult. Attachment relationships that come after reflect the child's experience of care and protection from other adults. These attachment relationships reflect the child's experience of care and protection from that adult, but are also influenced by the child's experience of prior attachment relationships; especially primary attachment relationships. It is worth noting that each attachment relationship can can differ along the dimension of attachment security.
Attachment style reflects the child's overall approach to life and relationships, based on past and contemporary attachment relationships. It reflects their relative security when navigating their world and relationships.
When attachment relationships have gone awry, the child needs other attachment relationships to be especially good, and/or many positive attachment relationships, to support an overall secure attachment style.
In consideration of this, the role and importance of birth parent attachments requires new thinking in the child protection sector. Relational repair with birth parents may represent the best chance for children and young people to approach life and relationships in a secure manner.