This is the bigger part of the story, much bigger than Manafort and Gates.
George Papadopoulos, the foreign policy advisor for the Trump campaign, pleaded guilty to lying to the FBI in order to cover up Trump/Russia collusion. And he's testifying that the Trump campaign was actively colluding with the Russians to get illegal information.
https://assets.documentcloud.org/documents/4163402/Papadopoulos-Statement-Offense.pdf
That buries the "But it all has nothing to do with Trump!" meme. The Trump campaign was colluding with the Russians, and anyone denying it is lying.
At this stage, the best response of the Trumpflakes will be "But ... but ... you can't say Trump himself knew about it!". Yeah, good luck with that. You can get the FOX News dopes to buy it, but Mueller isn't that freakin' stupid. He knows the game. Work up the chain. Use the testimony of the small fish to build an ironclad case against the bigger fish above them, then use them to get bigger fish, and so on.