He has to find something, in order to justify his salary, budget, and effort.
It's a bit like the ritual of Pesach (Passover), where the wife removes all the leavening from the home except for one small amount, so that the husband, when he comes upon it, can prove that he was really looking hard for it. Somebody's head is going to roll, someone is going to end up in prison, for some silly reason that will actually have nothing to do with the original charges, and when that happens, there will be a full-court press to either impeach Trump or emasculate him for the remainder of his term.
Finding no crimes committed is something
Special Counsel John Danforth did not have a problem finding there were no crimes in Janet Reno’s handling of the Waco Massacre.
“He has to find something, in order to justify his salary, budget, and effort.”
He finds collusion between Russia, the Clinton campaign and the DNC to take down Sanders in the primary. And for that he gets a job in the administration.
As far as finding nothing, if that happens the rats will say it is because he was hired by Sessions and that is part of Trump’s team.