30% isn't 'most people'.Mainstream
the ideas, attitudes, or activities that are shared by most people and regarded as normal or conventional.
'Heard of', probably loads. Exactly the same way that I think a lot of people might know the word 'Charizard', like they might know the words 'Jon Snow' (and no, I don't mean the British Broadcaster). I think a lot of people would know what the words 'Space Marine' are. A lot of people know what 'Orks' are. Once you start showing them pictures of Tyranids and Necrons (i.e; Xenomorphs and Terminators), that's when things will start to fall apart.What percentage of people in the US do you think have even heard of warhammer?
But, just 'cause you know what something is, doesn't mean you're a 'fan' of it, and it definitely doesn't mean that you're invested in it.
Every Pokémon is a Pikachu, even the ones that aren't.