@rangerrebewFusion GPS was an opposition research group. These type companies abound across the United States as candidates across the country need to know the background of those running against them. I knew, worked a few months with, the owner of a successful opposition research company in Austin, Texas, who did opposition research and used election data to determine what a candidate in his/her district needed to do to get elected. I did the election numbers/history of our county and sent it to him for comment. His response was, could he have my research for his company; that I had done it correctly. I knew if he said that, I could depend on my work to be right.
Fusion GPS was an opposition research company, based in Washington, D.C. Both Republicans and Democrats used this company at the beginning of the last presidential election.
Christopher Steele worked for Fusion doing investigations. Mr. Steele had also worked with the FBI at times and was known by them to give them correct investigation information. In other words, they trusted his work.
The Democrat Party paid Fusion for opposition research. They had no idea what might be found which is why they paid them to do the research. When Steele found the Russians may have compromised Trump due to Trump's stay in Russia, he gave the information to the FBI for them to determine if the information was correct. The FBI took the information, again, since Steele had worked with them and they knew his work to be credible. When this information came to McCain, he did not know the FBI had it, so he sent it to them to determine if it was true or not.