How do you define a hardcore fan?
Joe Rogan is the Godfather of the so called "hardcore fans" and even he doesn't follow MMA religiously. On the other hand, you have Ariel Helwani (who is vehemently hated by many hardcore fans) who can remember UFC numbers and headlines like the back of his hand.
Also GSP, the most noncontroversial GOAT, doesn't follow MMA religiously. He recently said it on the JRE podcast. He follows a few guys he respects, and the rest he doesn't care for.
All these labels of "hardcore fan" and "casual fan" are just meaningless labels used to create an elitist delusion in some people's minds. It is similar to Right Wingers calling Left Wingers "Libtards" "SJWs" "Cucks" and etc, and Left Wingers calling Right Wingers "NAZIs" "Facist" "Racist" and etc.
They are just distractions that are used to hide a weak position and/or to impede productive conversations.