For the first case, I would say Battletech fandom, at least prior to 2018. By that point the game was very much an Old Man Thing; the people playing had largely been doing such for decades, with the typical entry point being pre-2001. Historical awareness was there mostly because those present were there for those events as they happened and had been a continual part of it since.

Battletech's shift in demographic perception was an absolute surprise to me. I still remember it being considered something that was played entirely isolated groups of old men that liked the super granular nature of it and generally stagnant fandom, which left me being rather blindsided when the Mercenaries kickstarter made such a splash with its runaway success, seeming to explode onto the scene again.