On Apollo 8, following the first trans-Earth injection, when the crew came back into contact with Houston, Lovell said: "Please be informed there is a Santa Claus." (Transcript)
Given that Apollo 8 had already been in contact with ground through Christmas Eve, what prompted Lovell to make this statement at the time that he did?
Note: Since motivations cannot be known without the account of the individual, I will take common sense answers speculating on likely reasons that include a statement to the effect that we cannot truly know why he did it. That's assuming we don't have an account from Lovell, of course.