I found a useful timeline posted at JustSecurity.Org and jotted down my thoughts (both on the situation and on the timeline's wording) to clarify things in my own mind. I only looked at the period from early 2014 through April 4, 2016, because that was enough to digest. Please look at the original timeline because my interpretation of events might be slightly different from theirs.
To set the stage: By March, 2014, under the Obama administration, Russia had invaded and annexed Ukrainian territory (the Crimea and portions of eastern Ukraine); Ukraine had a reputation as being a corrupt place; and Burisma was Ukraine's largest private oil and gas extracting company. Mykola Zlochevskiy, who may be considered an oligarch, was Burisma's founder and majority shareholder. He had also held various high-level Ukraine government posts.
April 2014: The United Kingdom's Serious Fraud Office blocks the bank accounts of Mykola Zlochevskiy, who was suspected of corruption during the ousted pro-Russia Yanukovych regime. Under a commitment made to the Ukraine government to recover assets allegedly stolen out of the country, the US had investigators work on the case against Mr. Zlochevskiy with Ukrainian investigators.
Also April 2014: Hunter Biden, son of then-US Vice-President Joe Biden (who was the US "point man" on Ukraine policy), "joins" Burisma's board of directors after having been discharged from the Navy just months earlier for testing positive for cocaine. Per Burisma Holdings, Hunter Biden was placed “in charge of the Holdings’ legal unit ..."
- "Joins?" People don't just "join" a board - they are appointed by the shareholders. And since Mr. Zlochevskiy was the majority shareholder, Mr. Zlochevskiy put Hunter Biden on his board.
- Since US investigators were involved, why would Zlochevskiy's appointment of the then-VP's son NOT have a "chilling effect" on their desire to investigate Zlochevskiy?
May - June 2014: Petro Poroshenko succeeds to the Ukrainian presidency following election on a platform of turning Ukraine back to the West.
August 2014: Ukrainian Prosecutor General Vitaly Yarema opens an investigation of Zlochevskiy.
October 2014: Under pressure from the US and "other international backers," the Ukraine Parliament establishes the "National Anti-Corruption Bureau" (NABU) in exchange for financial aid.
- Given the Ukraine's bad reputation, the US and "other international backers" had reason to be concerned that their aid might be frittered away by corruption. However, should it not be acknowledged that the insistence on NABU's creation was, to some degree, dictating how Ukraine was to run its internal affairs?
- Does the US scolding of a lower-level Ukrainian prosecutor, bother you?
- If you were that Ukranian prosecutor, would the fact that VP Biden's son continued as a high-level hire of Zlochevskiy send a conflicting message, at least insofar as an investigation of Zlochevskiy/Burisma is concerned?
- One prosecutor knocked off. Score one victory for Zlochevskiy.
- If a letter of "no case" was sent to Zlochevskiy's attorneys, would Hunter Biden, as a hire of Zlochevskiy in charge of Burisma Holdings' legal unit, have had some involvement with it?
- Do the US Ambassador's demand for termination of Ukraine officials, and his alleged interest in how the Zlochevsky case was handled, bother you as meddling in Ukraine's internal affairs?
- Again, did the fact that then-VP Biden's son continued as a high-level hire of Zlochevskiy send a message conflicting with VP Biden's public statements?
- Score a second victory for Zlochevskiy in getting letters out of the Ukraine government stating Ukraine had no case against him.
- Why/How is it Ms. Nuland's business to determine what "serves the citizens of Ukraine?" Isn't that "the citizens of Ukraine" decision through their electoral process? At this point was the US 'helping' Ukraine combat corruption, or meddling in its internal affairs?
- Again, did the fact that then-VP Biden's son continued in the employ of and received pay from Zlochevsky, an oligarch, send a conflicting message?
- Why wouldn't investigation of Zlochevskiy's Burisma lie dormant as long as Hunter Biden was in charge of its legal unit, and the then-VP Biden had apparent control over vital US aid to Ukraine?
- Would anyone in Ukraine's government want to risk the hundreds of millions in US aid cited by then-VP Biden by taking an action that could lead to his son losing an almost 7-figure-a-year job?
- Score a third victory for Zlochevskiy in a second prosecutor getting fired.
- But there were "investigations" being conducted by the PGO -- just not the ones desired by the then-US government. Kent's letter, therefore, lends credence to Solomon's story that the last US administration did not want the "Anti-Corruption Action Centre" (Ant-AC) investigated. (Ant-AC is, apparently, a joint venture between various US officials spending US taxpayer money and George Soros.)
- While there was a US concern over "corruption" by Ukrainian oligarchs, the Ukrainians, via their then-duly elected government, seem to have had greater concern over corruption fostered by US and other foreign entities' meddling in Ukrainian affairs.
The above timeline demonstrates that Mr. Zlochevskiy made a brilliant move by hiring the then-US VP's son for his company's board, because the "appearance of impropriety" was followed by (1) a lack of interest in investigating Zlochevskiy/Burisma and (2) essentially a letter of exoneration from the Ukranian government. The fact that then-VP Biden did nothing to cure the "appearance of impropriety" (and there were many things that he could have easily done) speaks volumes.
The above timeline also demonstrates a shocking involvement of the then-US government and "other international backers" in the Ukraine's internal affairs, justifying the PGO's investigation of entities and individuals involved in US-supported "anti-corruption projects."
The "cognitive dissonance" of US officials criticizing Ukraine for not going after Zlochevskiy/Burisma, while the then-VP's son continued in the employ of Zlochevskiy/Burisma, would be a potent distraction from what the Obama Administration plus "other international backers" were doing in Ukraine via the Ant-AC organization.
There is plenty that went on in the Ukraine, including actions by US officials - many of whom continued in office under the Trump administration, that needs investigating.