Faithfully discharging the duties of one's office is seemingly an ancient oath.
Conflicts of interest and Russian meddling in our democracy simply were not deemed worthy of oversight by the GOP. [Power is everything]
I do agree that the passage of time has hurt the political viability of a Democrat led investigation (assuming the Democrats take the House, which is not a given). Most Americans seemingly do not care, and would prefer that Congress address issues impacting day-to-day concerns that Americans encounter. Congress can juggle more than one ball, but politically, the nation looking towards 2020 more and more.
Matters of principle or moral integrity, take a back seat to our portfolios, our taxes, and comforts. We have stopped asking ourselves the more difficult questions.