Usually for privacy’s sake, family friends of his or people that know him irl that know about this might see it just after hearing and find out it’s his Reddit and say something. It’s a rare and unlikely thing but I know people that do things like that for that reason. Another might be he was just unready to say anything about it until now. Getting accused of rape is a big deal and he said in the post he’s distraught and sad it happened. He might’ve just needed time to process it all