Maybe I only speak for myself when I say this: but interest in the unexplained comes and goes. Sometimes I really don't care for discussing unexplained phenomena, others I don't sleep and spend my time compiling and organising all the sources I can find on the topic :D There's maybe also the fact that this isn't a convential kind of social media; people spend more time on applications that they get direct notifications from, and especially on social media that don't require a lot of thought. Also, I've found that it gets a bit depressing after a while, and I guess sometimes people aren't always in the mood for that. Sure, I never knew the group personally, but reading about them and how full of ambition and youth they were knowing that they died so young is... depressing, to say the least. Sometimes I just don't have the energy to think about that, I guess, but maybe that's just me.
Don't be creeped out though, I don't think any of us have been kidnapped to be questioned by the CIA :D or at least not yet