@mystery-ak
Remember it was a Republican candidate who first hired Fusion GPS for opposition research. Knowledge of the dossier was found in their research. When one hires such a company, one doesn't know what they will find - that is why one hires them, to see what is there. Numerous people hired Fusion GPS and they did their job - opposition research.
But it was the Dems and Hillary who paid Fusion to up the game and interview former Russian KGB operatives, who made up slanderous allegations against Trump, so bad that even Brennan thought it was bunk.
Then it was the Obama admin, who also ponied up nearly a million to the law firm who hired Fusion, at about the same time the DNC and Hillary kicked in, who then used that fake dossier to corruptly and criminally abuse the institutions of the FedGov to open up investigations, get wiretaps, and get subpoenas on/from members of the Trump circle. High crimes and misdemeanors that make the Nixon admin look like choir boys.
It was also that fake document that is the basis of the Mueller investigation.