To understand, first look at Soros and Buffett's Politics. In both cases they support wealth redistribution, egalitarian government intervention, and the party that most supports these things.
Next, look at what they have actually done in their careers. Buffett is a master of using tax various shields, he benefits mightily from the inheritance tax by being able to buy family businesses on the cheap, plus via his insurance operations (among the biggest supporters of estate taxes are insurance companies), and his estate will never be fully taxed as he is putting almost all of it in a charitable foundation. Soros, I believe was grandfathered in with his offshore fund such that only the income he pays to himself in the USA is taxed, much of the rest of his investment gains have been highly tax advantaged offshore. Yet he supports the left and statism at every turn, including rabble-rousing street activists.
It appears that in 2008, Buffett was paid back in spades with many crony-capitalist investment opportunities. Soros likely has benefited from personal contact with all the top bureaucrats, etc, to get inside info on policy changes.
Would either of these men had had such opportunities if they had been, say, staunch libertarians?
The basic idea is that these big players are crony-capitalists who work the system to thwart competition, while then finding ways to exclude themselves from the policies that they advocate for.
You deserve credit for novelty at least.