There are two separate stories that center around Fusion GPS and no one seems willing to stitch them together.
Originally hired by "Never Trumper" republicans, Fusion GPS started working for the Democrats in May 2016 after Trump win the nomination. Fusion GPS's work eventually became what is now known as the Golden Showers anti-Trump dossier that has mostly been debunked.
Fusion GPS was present for the Trump Jr./Russian lawyer meeting in June 2016. The media is currently saying this is a smoking gun and Fusion GPS are Russians.
There's only two ways these these stories can coexist.
1) Fusion GPS are not Russian Agents. They were making opposition research for the Dems and the June meeting was a sting to try to entrap the campaign.
2) Fusion GPS are Russian agents and the Dems coordinated with them to take down their opponent's campaign... Exactly what Trump is accused of.