A previous question mentioned Rav Moshe Feinstein permitted an Ashkenazi to make a wedding during Sfirat Haomer after Lag Baomer. What might have the circumstances been?

Even an Ashkenazi with a previous custom to observe sphira until Shavuot may make a wedding earlier when it is a widower with small children. In general Rav Moshe was very lenient about changing from one custom of sephira to another, and attending weddings against one's own custom if it is the custom of the bride and groom.