First, the active motivation to believe.

For the family, particularly Beverly Dollarhide, accepting this person as Nicholas was necessary for psychological reasons.

The alternative was too painful.

Active skepticism would have required confronting not just the possibility that this was an impostor, but the accompanying questions: where was Nicholas, was he alive, had he suffered, would they ever know?

Second, the social momentum of established fact.

Once Carey had brought “Nicholas” home and the community had responded to his return, the social reality of his presence was established.