Conspiracy
Despite its ominous sound, the federal charge of conspiracy has a low bar to clear. If two people agree to commit any federal crime and if they undertake any, however trivial, overt act to further the plan, they can be charged and sent to prison for up to five years, even if they never actually committed the contemplated crime.
In other words, when Mueller and his buddies arranged for George Papadapoulos to receive $10,000 through strange circumstances and then Staked out the Airport, detained and searched him, finding NOTHING,
EVERY PERSON INVOLVED WAS ENGAGED IN A CONSPIRACY TO LAUNDER MONEY
Conspiracy to defraud the US government has a very low standard. Causing a bureaucrat to spend extra time by failing to volunteer information is an example of such a crime.