You cannot understand the left if you do not understand that Leftism is a religion. People who believe in Leftism have as many dogmas as the most fundamentalist Christian.
One of them is material equality as the preeminent moral goal. Another is the villainy of corporations. The bigger the corporation, the greater the villainy. Thus, instead of the devil, the left has Big Pharma, Big Tobacco, Big Oil, the "military-industrial complex," and the like. Meanwhile, Big Labor, Big Trial Lawyers, and, of course, Big Government are leftwing angels.
No rational person can deny that big governments have caused almost all the great evils of the last century, arguably the bloodiest in history. Whatever bad big corporations have done is dwarfed by the monstrous crimes, the mass enslavement of people, the deprivation of the most basic human rights, not to mention the mass murder and torture and genocide -- committed by big governments.
How can anyone who thinks rationally believe that big corporations rather than big governments pose the greatest threat to humanity? The answer is that it takes a mind distorted by leftist dogma. If there is another explanation, I do not know what it is.