Because nothing plus nothing equals nothing.Any entity can conduct an investigation.. They can investigate a ham sandwich for Christ's sake.What goes around comes around. President Clinton was impeached for misleading a grand jury about sexual peccadilloes; Four*** of those (at least) who voted to impeach the Pres. later resigned for more egregious sexual activities.
Washingtonpost.com Special Report: Clinton Accused
Gingrich, Hyde, Livingston, Foley
Now, before the investigation of Trump's possible obstruction of the inquiry into Russia's effort to impact the election of Nov. 2016, an effort is being made to obstruct this effort by Trump's surrogates, and even his attorney's, press Sect's and members of his administration who have not been forth coming. The AG of the US clearly mislead the Congress when under oath he said I can't remember and other words to that effect doznes of times during six hours of testimony.
Comey was fired by the POTUS. POTUS has absolute discretion to do so.
This investigation is going to lead to nothing.
But.....if it makes you orgasmic, so be it.
Why do you believe the investigation will lead to nothing?