I'm sure sour-grape Vindman is sore at Trump for not falling down before him in the impeachment boondoggle, and resents being dismissed. But Vindman had a history of problems the democrats refuse to talk about. He was a bloated egotistical buffoon filled with his own supposed importance and standing. There are many examples. You mention his responsibilities as a diplomat. Vindman referred to himself as a diplomat with great importance in fashioning and implementing US diplomatic policy in Ukraine. That was a bunch of crap. Trump dictated policy and Vindman dismissed it like a tin-pot rebel insurrectionist.
Here is how the egotistical buffoon honored himself in testimony before Congress: "For over 20 years as an active duty United States Military Officer and diplomat, I have served this country in a nonpartisan manner..."
https://apps.npr.org/documents/document.html?id=6543468-Alexander-Vindman-Testimony
Is he stupid? He would have to be to think he was non-partisan or even a diplomat. What an egotistical moron. Although in further testimony he claimed he conducted diplomatic talks with Zelensky, that was never his job and he never actually did it anyway, he was just lying to make himself look good, the egotistical buffoon. He claimed to be a diplomat? Was that true? Only in the thinnest stretch of the term, and then his position was not very flattering in reality in terms of diplomatic title. Let's look at the real diplomat titles in foreign service. The diplomat body assigned to a foreign nation has as its head the Ambassador. Below that is what is called the Minister. Below that is what is called the Minister-Counsellor. Below that is the First Secretary. Below that is the Second Secretary. Below that is the Third Secretary. And, finally, right above the Assistant Attache is the Military Attache.
In modern diplomatic practice, there are a number of diplomatic ranks below Ambassador. Since most missions are now headed by an ambassador, these ranks now rarely indicate a mission's (or its host nation's) relative importance, but rather reflect the diplomat's individual seniority within their own nation's diplomatic career path and in the diplomatic corps in the host nation:
Ambassador (High Commissioner in Commonwealth missions to other Commonwealth countries); ambassador at large
Minister
Minister-Counsellor
Counsellor
First Secretary
Second Secretary
Third Secretary
Attaché
Assistant Attaché
The term attaché is used for any diplomatic agent who does not fit in the standard diplomatic ranks, often because they are not (or were not traditionally) members of the sending country's diplomatic service or foreign ministry, and were therefore only "attached" to the diplomatic mission.
Diplomatic rank - Wikipedia