From Private Ryan to MASH...I remember there was this one episode that tracked a series of trades and deals. I think Radar was trying to get Potter some tomato juice, or something like that, and Klinger gave up some stockings for a weekend pass...I don't know; it's been a while. But I think the plot of this fuckery resembles that episode a lot more than any grand scheme with evil geniuses operating behind the scenes. Different assholes with different motivations, with Lev in the middle of it trying to deal out favors and money to make it happen. Look at the different characters on what they want, and what they can provide.
Lev/Igor: One of the big mischaracterizations is that they were working for Rudy, that they were his henchmen. They weren't. They were getting paid by Firtash, and they were paying Rudy, not the other way around. Henchmen don't pay their masters. I think they were basically small time grifters, who Firtash used because they had US citizenship. As the story continued, they may have cut side deals for their own profit, but their main loyalty was (and probably still is) to Firtash. They want cash, and they do the work to put deals together.
Rudy: You all remember Cohen. In addition to the stuff that got him sent to prison, he was also getting paid by various corporations - domestic and foreign - to influence Trump. In another era, this would have been a scandal in and of itself. When Cohen went to prison, I think Rudy saw a business opportunity, and that is how I see his role in this -working Trump for his clients' advantage. He's rich, but he's not Firtash/oligarch/oilman rich. He is working for a fee, not a grand investment opportunity this corruption will allow. He wants cash, and can provide influence in the White House.
Firtash: Currently waiting extradition to the US for unrelated corruption in an Indian deal. Obviously, he wants some influence in the DOJ to slow that down. Less obviously...in January 2019, Poroshenko's government was moving to make changes to the Naftogaz board and to forgive 100s of millions of dollars that Firtash owed. Can you guess who squashed it? Marie Yovanovitch, carrying out the official US policy and seeing these moves as backsliding towards corruption. Yovanovitch had previously worked against such moves that she (...we...the US) believed would result in more corruption. As early as 2016, she countered a move to turn over the state owned pipeline to Ukrtransgaz. Part of her work was fighting corruption in the energy sector. Firtash was a corrupt guy in the energy sector. Firtash wanted her gone, and he can provide cash and connections in Ukraine.
Trump: This is the part that everyone is focused on. Trump wanted a politically damaging investigation of Burisma and Bidens publicly announced, and he wanted to undermine the conclusion that Russia interfered in the 2016 election. He also wanted payback for Ukrainians who provided evidence against Manafort. He can provide control of the US Embassy in Ukraine, funding to Ukraine, weapons, control of the DOJ, sanctions on Nordstream II, etc...I get heartburn just typing that all out.
Perry, and the oilmen behind Perry: They want to export liquified natural gas. There are few things that will help that, including changes in the Naftogaz board and blocking Nordstream 2. They can provide money to the campaign of anyone that helps with that.
Prosecutor General Lutshenko. The PG's office was under scrutiny for a long time, even prior to Lutshenko. Under US pressure, Ukraine started the NABU (National Anti-Corruption Bureau) which was a rival group that focused on corruption. Yovanovitch, continuing with the US policy on anti-corruption, continued to criticize the PG's office, including specific officers under Lutshenko. When Zelensky won, he was asked who would be his PG, and he quipped something like "I don't know, but it won't start with L and rhyme with utshenko." Lutshenko wanted Yovanovitch fired, and could provide a public announcement of a Burisma/Biden investigation. He did, in fact, announce they were reopening the investigation into Burisma in March of 2019. This was the same time that Solomon ran the hit pieces on Yovanovitch, quoting Lutshenko. Yovanovitch was fired on 4/24, about a month later. But Zelensky was elected on 4/21, which meant Lutshenko wasn't going to be in position to do much about an investigation.
So, I think Trump traded the removal of Yovanovitch for the investigation of Burisma. But he didn't really get paid in full. Lutshenko's later backed off his statements, and Zelensky was now in control of the government anyway. So, on the Art of the Deal Part 2, he didn't want some Prosecutor General working with The Hill, he wanted the President of Ukraine to "get in front of a microphone" to announce the investigations. The removal of Yovanovitch opens the way for the oilmen and Ukrainian oligarchs working with Lev/Parnas and Perry to try to restructure the Ukrainian energy sector to allows for easier access to markets (for the oilmen) and easier ability to skim the profits (for the oligarchs.) It's just a collection of greedy fucking morons.