I agree that it most likely is in the best interests for those in power to just drop the assassination story and pretend it never happened, but if it is the best choice it's the best in a series of bad choices for the powerful. Underneath the immediate concern of one of the peonage getting up the courage to kill one of the Princes of the Universe is the general public response.

Every day the assassin stays free and in the news is a day everyone can see that the American public supports and condones the killing of people in C-suite (and likely beyond C-suite). That is one hell of a permission structure now in place. If the Powers That Be then pretend the killing didn't even happen letting the assassin off the hook, that's them giving carte blanche to copycats to do as they will, nobody is going to stop you. Nothing is true, everything is permitted.

I misspoke, unanimous consent isn't required, but it makes the process much smoother, and is considered the "normal" means of ratifying committee assignments.

For Diane Feinstein to resign from the Judiciary Committee and for appointing someone else to the committee right now requires unanimous consent, and the Democrats are not going to get that from the Republicans right now. Regardless, the act of replacing someone on a committee is subject to debate and can be filibustered. If Diane Feinstein were to retire or die, that's it, a 10-10 split in the Judiciary Committee until the next Congress, so long as the Republicans refuse to play ball.