Personally, I do not think that the defection of oligarchs was key to the downfall of the Yanukovych presidency. While the defections may have played a role, I think that the main causes of Yanukovych's downfall was the violence and actions of snipers in particular that made the deal reached
with western powers a non-starter. However, it is always possible that it was one of the oligarchs that hired the snipers as there is evidence
that it might not have been Yanukovych. The street decided that Yanukovych had to go. However, the final blow that made Yanukovych's continued presidency impossible was the defection of many security forces who simply refused to confront the protests. Yanukovich lost the power to have his orders enforced and that is the immediate cause of why he was toppled. For the most part the oligarchs either foresaw this beforehand and abandoned him or did so later when he fled.
argues that it was the fact that the oligarchs jumped ship which led to Yanukovich leaving power:
Viktor Yanukovich did not leave Kiev in the middle of the night because of a military invasion of his country, nor because the few armed militants in Maidan represented such a threat to his security that he had to abandon his lavish lifestyle.
No, he fled because the powerful Ukrainian oligarchs turned their back on him in fear of economic sanctions from Europe that would have meant the end of their industrial empire and freedom of movement.
While I disagree with Piet about the causes of Yanukovich's downfall, his account of the manner in which the oligarchs changed their allegiances and allied themselves with the protests and then the new government is quite interesting. Very early on, Piet notes
, Victor Pinchuk, a liberal-minded oligarch and son-in law of the first Ukrainian president and Russian ally Leonid Kuchma, signed a letter that supported the demonstrators. Pinchuk supports greater linkage with Europe seeing this as the "way to modernise the country, to fight corruption, the way to have a fair court, freedom of press, democracy." An even worse turn was the defection of Rinat Akhmetov one of the 40 wealthiest men in the world who wanted to reopen negotiations with the EU to have balanced agreements with both Russia and Europe. Another prominent oligarch supporter of the opposition is Petro Poroshenko
who is into shipping, confectionery, and agriculture. He owns a television station that dutifully covered the revolution in Independence Square around the clock.
Even Eastern Ukrainian billionaires
Igor Kolomoyski and Sergey Taruta who had been close to Yanukovych supported the new government and the new prime minister. They were rewarded with governor positions in pro-Russian regions of Donetsk and Dnipropetrovsk. Both have strong ties to European business interests as Piet shows. The last thing they wanted was to face possible economic sanctions or being unable to travel to vacation in Europe and hob-knob with European business elites. A New York Times article
sums up in a short paragraph the origin of the Ukrainian oligarchs and their role in Ukrainian politics:
Like other tycoons scattered throughout post-Soviet countries, Ukraine’s rich capitalized on the flawed privatization of publicly held assets to establish enormous fortunes, presiding over news media, banking, telecommunications, steel, coal and heavy industry empires. But in contrast to Russia, where President Vladimir V. Putin has barred the oligarchs from politics, Ukraine’s wealthy clans retain enormous influence, acting as a shadow cabinet with identifiable factions in Parliament. Mr. Poroshenko is himself a member of Parliament.
In Russia I expect that the oligarch's are still quite active but that they are careful not to cross Putin.
There is much more in Piet's article that is well worth reading in its entirety. He notes that Russian oligarchs were no doubt alarmed at the fall of the rouble with the threat of sanctions looming. However, there are also western business interests in Russia who certainly do no want disruption of their activities that could hurt their profits. The oligarchs from both countries no doubt want stability rather than conflict that could hurt profits. What they do not want is reform that decreases their economic and political power. They will be quite willing to help the IMF and others to impose austerity measures and economic reforms such as doing away with subsidies as a price of having the Ukraine economy rescued from bankruptcy.