If Mueller asked the judge for 10 days to submit a report on Manafort's cooperation, Mueller could have purposely been waiting for Trump to submit the written answers to him, then discuss Trump's answers and other related stuff with Manafort in one last effort to get Manafort to tell the truth. Manafort and Trump supposedly have a joint defense agreement so if Mueller is saying Manafort lied today, Trump may have lied too and they may have plotted together with the promise of a pardon or a commuted sentence. (Doesn't help with possible state charges)
This would also imply that Gates, Flynn and Cohen have told almost everything, provided a lot of documentation (in addition to what Mueller already has on his own) and continue to be very strong witnesses.
This would also imply that Gates, Flynn and Cohen have told almost everything, provided a lot of documentation (in addition to what Mueller already has on his own) and continue to be very strong witnesses.