I believe that he was actually primus all along, but the vampiric side was his was sort of “locked away” and eugene was the key to unlock it. As shown in the ritual; there was both a red and blue light that connected the two, just like eugene and him. Hope it makes sense idk! (づ￣ ³￣)づ
I honestly understand that it was harsh but considering the age gap, he was too immature to handle their relationship….