I don't think they were the same person.
WhiteNat did kind of have multiple personalities, kind of hard to pin him down. He sure did seem like IncognitoGuy's alt there for awhile when he was behaving himself better and being more professional, though now I'm not so sure. Maybe he just got increasingly frustrated and amped up the racism/homophobia/trolling accordingly.
M00nMan.exe was the same memer as another account who went by Gorthaur, who was being a Neo-Nazi on politics stream before he got banned from Imgflip the first time. (I was also involved in helping that account get banned). He is more of a hardcore Neo-Nazi. WhiteNat kind of followed in his lead a bit, almost like WhiteNat was being groomed by him.
I don't know why either of them got so interested in IMGFLIP_PRESIDENTS tbh. If they had just kept to themselves they probably would still be here.