Let me start by saying that Trump IS a crook and has been a crook all his life. The task of the FBI is to prove without a shadow of a doubt that he's a crook. Roger Stone is a self-professed 'dirty trickster' and has been employing shady campaign tactics since the early 1980'd when he, Manafort and Lee Atwater started their lobbying firm. He's a serial liar just as Trump, Manafort, Flynn, Popadopoulis and Gates are. A leopard never changes his spots.
Opposition research is normal and legal. What is illegal are litigious accusations that damage a person's character or credibility by perpetrating stories that are nothing but false allegations and the hacking into personal computers by a foreign adversary to the United States is the culprit of that hacking.
So far, the FBI investigation under the direction of Robert Mueller has resulted in ;
Paul Manafort - indicted
Michael Cohen - pleaded guilty
Michael Flynn - pleaded guilty
George Papadopoulos - pleaded guilty
Rick gates - pleaded guilty
Alex Van der Zwaan - pleaded guilty
Richard Pinedo - pleaded guilty
Konstantin Kilmnik -indicted
Roger Stone - indicted
13 Russian Nationals - indicted
12 Russian Military Officers - indicted
An example of voter suppression propagated by Russian trolls. People were encouraged to 'tweet' their vote using a link, of course that's illegal but people believed they could do that. Many 'votes' for HRC were made this way which of course negated their vote entirely.
Here's another example of Russian 'click-bait'.