He didn't. IIRC McFarlane only owned (or thought he did) the MM logo and maybe the likeness of the character but not any of the previous stories due to the legal quagmire the rights were in. This was basically him trying to get some money out of it and piss off Gaimen (who was suing him at the time) by waving the logo in his face.
Of course then the writer of Spawn at the time completely changed Man of Miracles to look like a white-haired anime character before revealing that "he" was actually both Jesus Christ and the mother of both God and the Devil (Man of Miracles = MoM, get it?) who had been reborn on Earth as Spawn's wife's twin children.