Stewart/Colbert would be the ticket to the greatest America.

Reagan and Trump. The former was a b-list actor before becoming governor and then president and the latter played a successful businessman in the fictional series "The Apprentice".

Trump and Reagan

What people need to understand about the Ukrainian oligarchs are that they're actually oligarchs. It's not US-style "we should get around to regulating campaign financing some time so that Google doesn't run candidates", it's not Russia-style "Actually you're a minor noble there to exploit your dedicated region for the Tsar, by appointment of the Tsar":

In Ukraine it's "businesspeople with not completely clean records running for office because that's a neat way to get legal immunity and corruption opportunities", aka actual oligarchy, with the fat cats themselves in office. They're absolutely not a unified front, often hate each other's guts both in a business and political sense, and while (at least for the longest time) the Ukrainian people had practically no say in who would run, they could choose which Oligarch they liked best, putting their thumb on the scales.

So why did Kolomoyskyi support Zelensky? There's a very simple explanation: Zelensky ran against Poroshenko, who Kolomoyskyi had quite a fallout over stuff much more important than politics, that being funnelling oil into to Kolomoyskyi's refineries:

On 25 March 2015, Ukrainian President Petro Poroshenko signed a decree dismissing Kolomoyskyi from the post of Dnipropetrovsk RSA Head, saying "Dnipropetrovsk region must remain a bastion of Ukraine in the East and protect peace". Kolomoyskyi was replaced by Valentyn Reznichenko.[31][120][121] This followed a struggle with Poroshenko for control of the state-owned oil pipeline operator.[122] After Poroshenko's dismissal of Oleksandr Lazorko, who was a protégé of Kolomoyskyi, as a chief executive of UkrTransNafta, Kolomoyskyi dispatched his private security guards to seize control of the company's headquarters and expel the new government-appointed management. While Lazorko was in charge the state-owned pipelines had been delivering oil to a Kolomoyskyi-owned refinery in preference to competitors.[31][123]

In a further move against Kolomoyskyi, Poroshenko replaced Kolomoisky's long-time business partner Ihor Palytsa as governor of neighboring Odesa Oblast with the former Georgian president, Mikheil Saakashvili. That appointment triggered a dramatic and public war of words between Kolomoyskyi and Saakashvili. Saakashvili told journalists Kolomoyskyi was a “gangster” and “smuggler.” Kolomoyskyi told them Saakashvili was “a dog without a muzzle” and “a snotty-nosed addict.”[124]

Kolomoyskyi responded that the only difference between Poroshenko and Yanukovych is “a good education, good English and lack of a criminal record.” Everything else is the same: “It’s the same blood, the same flesh reincarnated. If Yanukovych was a lumpen dictator, Poroshenko is the educated usurper, slave to his absolute power, craven to absolute power.”[125]

Enemy of my enemy and all that.

I can't really tell just how important access to Kolomoyskyi's TV channel was for Zelensky's campaign, the man was a folk hero way before meaning that vanishing on TV might've just boosted his youtube channel in equal amount.