It answers to criticisms of the impeachment efforts that imply, when they do not state outright, that since authority over foreign affairs is given to the Executive branch, Congress can't impeach the President for it or at least have any of the information they need to decide if impeachment is warranted.
So while dismissing a Cabinet member is entirely within the President's prerogative, if he exercises it inappropriately, Congress can impeach him for it. Likewise, the President can conduct foreign affairs, if he does so inappropriately, Congress can impeach him for it.
Uh, have you seen our commentary regarding "Obstruction of Congress" in this thread? They
can impeach, but many things take time to play out. The Democrats
decided they wanted this open and closed in just a handful of months, because they evidently see the impeachment hearing to be about eliminating a 2020 Presidential opponent, as I wouldn't be surprised if there is polling data to suggest that they have better odds against Pence than they do against Trump.
Compare this to the Watergate break-in and initial "Deep Throat" leak, in June of 1972,
A Senate investigation on the matter that starts in mid-May of 1973,
by mid-October the VP Spiro Agnew resigns due to corruption charges while Governor of Maryland. Just using the Senate hearings as a starting point, we're still in September on that timeline.
Ford is nominated as new VP.
October 20, 1973 the "Saturday Night Massacre" occurs.
November 17, 1973 Ford confirmed as new VP
And then I more blatantly theft from wiki rather than cherry-picking events and editing them slightly:
https://en.wikipedia.org/wiki/Timeline_of_the_Watergate_scandalJanuary 28, 1974: Nixon campaign aide Herbert Porter pleads guilty to perjury.
February 25, 1974: Nixon personal counsel Herbert Kalmbach pleads guilty to two charges of illegal campaign activities.
March 1, 1974: In an indictment against seven former presidential aides, delivered to Judge Sirica together with a sealed briefcase intended for the House Committee on the Judiciary, Nixon is named as an unindicted co-conspirator.
March 4, 1974: The "Watergate Seven" (Mitchell, Haldeman, Ehrlichman, Colson, Gordon C. Strachan, Robert Mardian, and Kenneth Parkinson) are formally indicted.
March 18, 1974: Judge Sirica orders the grand jury's sealed report to be sent to the House Committee on the Judiciary.
April 5, 1974: Dwight Chapin convicted of lying to a grand jury.
April 7, 1974: Ed Reinecke, Republican lieutenant governor of California, indicted on three charges of perjury before the Senate committee.
April 16, 1974: Special Prosecutor Jaworski issues a subpoena for 64 White House tapes.
April 30, 1974: White House releases edited transcripts of the Nixon tapes, but the House Judiciary Committee insists the actual tapes must be turned over.
May 9, 1974: Impeachment hearings begin before the House Judiciary Committee.
June 15, 1974: Woodward and Bernstein's book All the President's Men is published by Simon & Schuster (ISBN 0-671-21781-X).
July 24, 1974: United States v. Nixon decided: Nixon is ordered to give up tapes to investigators.
Congress moves to impeach Nixon.
-July 27 to July 30, 1974: House Judiciary Committee passes Articles of Impeachment.
-Early August 1974: A previously unknown tape from June 23, 1972 (recorded a few days after the break-in) documenting Nixon and Haldeman formulating a plan to block investigations is released. This recording later became known as the "Smoking Gun".
-Key Republican Senators tell Nixon that enough votes exist to convict him.
August 8, 1974: Nixon delivers his resignation speech in front of a nationally televised audience.
August 9, 1974: Nixon resigns from office. Gerald Ford becomes president.
September 8, 1974: President Ford ends the investigations by granting Nixon a pardon.
And in that quote block we Have March 1(unindicted co-conspirator for Nixon), or April 16th/30th for the Special Prosecutor and Congressional ask for the Watergate tapes. May 9th you have impeachment proceedings start, but it isn't until July 24th that SCotUS settles the tape dispute(going with the end of August start for Trump's stuff, that gives an equivalent of about mid-January, or points in time about now, or at the end of November. Now we can question why SCotUS seems to be so "comparatively slow" in handling the Trump Admins actions this time around, but people need to remember that the Trump admin doesn't control the Judicial Branch, so that part of things operates outside any timeline that either Congress or the Executive Branch can claim to control.
If Nixon isn't enough to compare against, I guess we could compare to the Whitewater investigation and the Ken Starr report:
https://en.wikipedia.org/wiki/Whitewater_controversyVince Foster's death occurs in July 1993.
April 22, 1994 - Hillary Clinton holds a press conference announcing she no longer objects to calling a special council to investigate Whitewater.
May 1994, Fiske issued a grand jury subpoena to the President and his wife for all documents relating to Madison Guaranty, with a deadline of 30 days. They were reported as missing by the Clintons. Almost two years later, the subpoenaed billing records of the Rose Law Firm were discovered in the Clintons' private residence in the White House, with fingerprints of Hillary Clinton, among others.
...
In August 1994, Kenneth Starr[30] was appointed by a three-judge panel to continue the Whitewater investigation, replacing Robert B. Fiske, who had been specially appointed by the attorney general, prior to the re-enactment of the Independent Counsel law. Fiske was replaced because he had been chosen and appointed by Janet Reno, Clinton's attorney general, creating a conflict of interest.
...
Starr drafted an impeachment referral to the House of Representatives in the fall of 1997, alleging that there was "substantial and credible evidence" that Bill Clinton had committed perjury regarding Hale's allegations.
...
By April 1998, diverted to some degree by the burgeoning Lewinsky scandal, Starr's investigations in Arkansas were winding down, with his Little Rock grand jury about to expire.[19] Hubbell, Jim Guy Tucker, and Susan McDougal had all refused to cooperate with Starr. Tucker and McDougal were later pardoned by President Clinton. When the Arkansas grand jury did conclude its work in May 1998, after 30 months in panel, it came up with only a contempt indictment against Susan McDougal.
Wow, if only Trump and company were held to the same standard, we might hear something in about 3 years? Heck, even Watergate itself took nearly 2 years to play itself out in full. But hey, the Democrats have found sufficient evidence this time that they're going to get the job done in 4 to 5 months.