Paradigm seems to be that since Clinton was a shoo-in, only Trump campaign was a suspect. Nobody would have thought that Clinton could have been colluding, so I bet nobody thought to investigate both campaigns equally.
-PJ
Comey himself was a victim of the "DC Bubble" that Nate Silver described, and structured the investigation on the premise that Clinton would win easily, so Russia would naturally hurt her and help Trump. He never thought Trump would win, and never considered investigating Clinton campaign potential outreach to Russia.
Paradigm seems to be that since Clinton was a shoo-in, only Trump campaign was a suspect. Nobody would have thought that Clinton could have been colluding, so I bet nobody thought to investigate both campaigns equally.
-PJ