Biden was late on the scene, after numerous US and EU officials pushed for Shokin's sacking because he was stymieing corruption investigations in Ukraine ie Biden was acting in an official capacity with his
quid pro quo.
It's all here (and in many other credible news sources):
https://www.ft.com/content/e1454ace-e61 ... 5a370481bc
In case it is firewalled:
EU diplomats working on Ukraine at the time have, however, told the FT that they were looking for ways to persuade Kiev to remove Mr Shokin well before Mr Biden entered the picture. The push for Mr Shokin’s removal was part of an international effort to bolster Ukraine’s institutions following Russia’s annexation of Crimea and the armed conflict in the eastern part of the country.
“All of us were really pushing [former Ukrainian president Petro] Poroshenko that he needs to do something, because the prosecutor was not following any of the corruption issues. He was really bad news,” said an EU diplomat involved in the discussions. “It was Biden who finally came in [and triggered it]. Biden was the most vocal, as the US usually is. But we were all literally complaining about the prosecutor.”
Mr Shokin had been appointed prosecutor-general of Ukraine in February 2015, but the discussions in Washington and EU capitals about pushing for his removal started as early as April after he failed to follow through on a burst of expected early anti-corruption moves, one former US Treasury official said. Mr Biden entered the fray in December 2015, placing Mr Shokin’s removal at the top of his agenda on a visit to Kiev. “I know how the idea to have Shokin fired came up, and it wasn't Biden. His direct involvement came late in the game,” the former US Treasury official said.
Trump's
quid quo pro, on the other hand, was trying to use already approved US government money as leverage to get dirt on a political opponent ie abuse of power.
Trump was also impeached for obstruction.