The call on the field had to be that he did not touch first base. It cannot be interference because the ball did not hit him. Being in fair territory is not enough to be called out after overruning first base. You have to make an attempt toward second base, which he never did. Even a slight attempt will be enough, but he didn't. Gotta just be a put out for not touching the base, which looked close on replay.
Just terrible luck that the guy backing up the throw was right there and made the attempt to tag him.