Thing is, Comey wasn't doing the investigation into the Russian hacking, he simply relayed the findings of the investigators that he thought were relevant and added his opinion. Face it, the head of the FBI is a lackey for the sitting president. Comey was trying to play both sides last year so he could keep his job. Ended up sticking his foot in his mouth a few times and pissed in everyone's cornflakes. It worked for awhile. Anyone can scribble BS on a sheet of paper and place it in a folder and send it to the Washington Post or whoever. The new age system is guilty, until proven innocent. Speculation rules the weak minds.
On another note, I hear the President farted at supper the other night.
Yet, all of this could be Trump being peeved that the "Russia thing" is just trying to delegitimize his government and he's not going to take it anymore. So he fires Comey for being one of those people in his way. Then he invites Russians into his office just to get in people's faces thinking, "This is such nonsense, I'm going to bring Russians into the Oval Office and send the press away, and to hell with all of you."

He is stupid and lazy and impulsive enough for that to be just as likely a scenario.