Intelligence/competence factor. Melania knows how to do the things herself that the wookie needed to hire 39 the people to do.
>Squeezing him to get dirt on Trump? Either fact or fiction
That's the only thing that makes sense to me. I think Mueller/RR figured they would use Manafort to cast aspersion on Trump. Manafort, having been exonerated already, was really in no danger, or so they said.
It may be, actually, that Manafort double-crossed Mueller/RR and fought back, knowing they had no case, so couldn't defend themselves. The shit started to hit the fan when Manafort began fighting back, because Mueller/RR were dead in the water with no ammo and the judge cleaned their clock.