1) Ukraine was and is one of the most corrupt countries on the planet.
2) In aiding and abetting the Euromaidan uprising and subsequent revolution and overthrow of the Ukraine government, the US was very closely involved in X% of what was going on, the planning, financing and operational actions that took place, including killings and determining those individuals who would ascend to power in government, finance and industry.
3) The overall US end of the Ukraine operation was honchoed by the wife (Victoria Nuland) of Robert Kagan, arch-neocon and rabid hater of Russia. Her boss was Hillary Clinton, who answered to Joe Biden and Barack Obama.
4) This cast of characters were up to their hips in everything that went on in Ukraine, including corruption, in which they became active if not fully willing partners by inheritance. Hunter Biden became involved up to his hips as well, though his motives were less "noble".
5) After the rebellion more or less succeeded - albeit with Russia scobbing off with Crimea and several large eastern provinces in tow - it fell to Donald Trump to pick up the shattered pieces.
6) Nobody on the planet, particularly in Europe, wanted to give or loan money to Ukraine because of the corruption.
7) Trump, having pledged to dis-involve the US from foreign wars and regime changes, was faced with a distasteful problem in Ukraine. It stunk to high heaven and he didn't really want anything to do with it.
8) The US, having already bought into the revolution and its finance, had very little leverage except for the corruption issues, and the fact that nobody else on Earth would touch Ukraine. So corruption was his leverage. Unfortunately, there was Hunter and Joe Biden already feasting on their kill and running the shop, their hands dripping in moolah.
9) In order to fund Ukraine and curtail the corruption, Trump and the new Ukrainian president had to gently ease the Bidens out of the picture.
10) When our domestic politics reached peak fury and the Mueller/Russia investigation collapsed, the strident left wing of the Democratic Party had very little left to impeach Trump for. But they were going to do it anyway, come hell or high water.
11) The Democratic left wing, also wanting to grab the presidency in 2020, wanted nothing to do with Joe Biden, vastly preferring those farther to the left. So they willing chose to sacrifice Biden when they decided they had to "make-do" with Ukraine as their reason for impeachment.
12) Republicans, fearing the lefties most of all, do not want to turn the Democratic Party over to the lefties by sacrificing - investigating - Joe Biden who has friends on both sides of the aisle. At least not right now they don't want to sac him.
13) So there is the dilemma. All this dirty laundry is starting to hang out of the basket, and the way forward is murky for all involved.[/SPOILER]