Manafort and Gates are accused of having played fast and loose with money and federal regulations — but their offenses actually precede their roles on the Trump campaign. Flynn pleaded guilty to lying to FBI agents about the substance of phone calls between him and the Russian ambassador — calls made weeks after the election.
That means Mueller doesn’t have the goods. Yet. If Mueller had evidence that This Specific Thing and That Specific Thing and the Other Specific Thing took place between the Trump campaign and Russian contacts in the summer and fall of 2016, those Things would be part and parcel of the indictments and pleas he would have reached already.
Instead, it appears he’s adopted a strategy of getting these guys with whatever he can get them for so that they might provide him with the details and the narrative he needs. In other words, the Flynn plea is part of a fishing expedition.