As I said before, the FBI was not investigating the Trump Campaign. The FBI was looking into certain people, like Carter Page, Roger Stone, Paul Manafort, and Michael Flynn, who had been investigated in the past and deemed to have suspicious relationships with Russian nationals, or were continuing those relationships immediately before Trump declared for office. carter Page was even considered to be a fully compromised asset of Russian intelligence.
None of these investigations would have come anywhere near the Trump campaign except for one thing. Donald Trump hired all of these people to work for him. One man, and one man only is to blame for the FBI now having questions about people working at the Trump campaign. The man who hired them.
Donald Trump.