Question: How much IC explanation will be given, and what will it be?
Answer: None, and nothing, until the plot is already underway. Sentience has been avoiding any reference to the plot because it doesn't want Acumen to know the details, and anything verbal will be overheard by Acumen.
No one who volunteered to help Sentience knew what they were signing up for, and no one is going to know in advance. So even the characters who are already committed to helping are doing so blindly.
If a currently uninvolved character sees the gathering, they can tag along out of curiosity, or because they are told in oblique terms that Shit Is Going Down. But there is no other explanation until we're already mid-coup and there's no turning back.