Why? Probably because all the bellyaching and whining about McConnell amounts to nothing in the grand scheme of things, so people lash out.
Short of dying while in office, McConnell will leave when he wants to leave.
Re: 6 - And if President Trump is re-elected, he is smart enough to know that the real power regarding legislation resides in the Senate. Which means that McConnell would call the shots if he is still the ML.