The trial against Manafort was by a jury. And if you read the...

The trial against Manafort was by a jury.

And if you read the articles, these jurors were a mix of Trump and anti-Trump supporters, and was accepted by the defence team. There were interviews of these jurors on Fox news and they (Trump supporters) said based on the evidence, Manafort was guilty!!!

So not where your allegation of biased is coming from.

In any case, the jurors convicted Manafort by the standard "beyond any reasonable doubt", after hearing all the evidence.

The judge only handed out the sentence - and if you had watch Fox news, they praised this judge before the trial, expecting him to rule in favour of Manafort as he was a conservative.