>>93250791I've got it.
The answer was there all along.
It's because Gura is actually a Leprechaun and has all of Myth + Fauna and Bae sworn to secrecy (though it doesn't really matter for Bae since she doesn't believe in Leprechauns).
Now that normally wouldn't be an issue, but then Leprechaun adjacent things started happened sans Poptarts story, so obviously none of them could talk about it.
Also that party at the beginning? Actually a Paranormal search party that got out of hand when Mori accidentally leaked that she was meeting with an Irish midget friend and raised some eyebrows from the cryptid-loving community.
Unfortunately that did not stop the following Leprechauny shenanigans from ensuing.
And they are still ensuing to this very day. That's why Gura can't stream. That's why Ame and Fauna had to leave.
Something's going on in the world of the Leprechauns, man.
And it's only a matter of time before the other Hololive girls get sucked in too (except Bae because Leprechauns don't real in Australia).