Whether the evidence pointed towards Russian attempts to influence the election or not, there should have been some notice given to the Trump campaign. In law enforcement, if you are setting up a sting operation to catch someone, you notify the would-be victim of your target. If you are setting up an undercover investigation, you don't tell them. Trump wasn't told that there would be someone working in his campaign. Res Ipso Loquitor, they were running some kind of undercover operation to investigate the Trump campaign for whatever motive, and now they are working mightily to cover it up.
As they tell us lowly tax-paying citizens when we object to a search: "If you don't have anything to hide, you have nothing to fear".