imo, Muller has got na-da and hes hoping someone flips.
The lamest ever was Fitz, who indicted Libby for lying to the FBI and Grand Jury about conversations he had with reporters, years ago. There was no underlying crime, so it was a ridiculous exercise (though obviously, not for Scooter Libby who lost his career and reputation as a result).
Mueller has already hit pay dirt with this indictment. He's got his scalp, and it looks to be a very legit one, in that Manafort was clearly a tax cheat. In a way, that's good for Trump - Mueller won't have to keep searching for someone, anyone, to convict of something, anything as Patrick Fitzgerald did with Libby.
The guilty of lying to the FBI plea that they got from the 30 year old dude is more worrisome for Trump, it is, at least vaguely campaign related.
But my overall sense is that none of those involved can flip on Trump because they don't know anything because, as Trump as said repeatedly, NOTHING HAPPENED.
It looks like Papadopoulos already has.