As Reuters and other outlets report, Ellis tore strips off Mueller team prosecutor Michael Dreeben who sought to try former Trump campaign manager Paul Manafort on a variety of bank fraud charges, several going back years before there was a Trump campaign. The article quotes Judge Ellis:
I don’t see what relationship this indictment has with anything the special counsel is authorized to investigate.Judge Ellis isn't patient with fishing expeditions, looking for what he called "leverage" on Manafort to force him to implicate Trump with Russians.
It’s unlikely you’re going to persuade me the special counsel has unfettered power to do whatever he wants.
It appears Mueller wishes to find enough dirt on Manafort to coerce him to say Trump colluded with Russians, whether it actually happened being immaterial.