Keep in mind that Manafort flipped, Flynn flipped, Gates flipped... hence they get some goodwill from Mueller when it comes to sentencing recs. Manafort hasn't been sentenced yet, it was delayed until his part in Mueller probe as asset is over.
Manafort flipped and then Mueller dropped the deal because he couldn't stop lying. He was also sharing info with Trumps legal team.
Also, Manafort has been sentenced for tax evasion, 5 years (I think). We are waiting on sentencing related to more charges currently.