Weird they released it so far from Christmas.
I can only assume because of the times. Fewer reels to go around, fewer theaters to be seen in. Wanting to build up momentum while it showed up through the holidays since there was no internet or home releases yet
It was released in June because they didn't want people to associate it with Christmas. Apparently back then Christmas movies didn't do very well, and they were afraid to jinx it. As I understand it they promoted it as a romance and did not feature Santa in the advertising. John Payne was promoted as the lead.
Fortunately it proved their fears were wrong. And since Edmund Gwynne wasn't the "main character" it garnered him an easy win for the Oscars.