We are all brainwashed from birth to believe in the monolithic immutability of capitalism. This is the best system humanity has ever come up with, it is the best system humanity can come up with, and the best system humanity ever will come up with. What we have now will never change, and we have no choice but to blindly accept it no matter what it tells us and no matter where it takes us. This is what we are told day and night.
It's a system predicated on strife and competition, where wealth is equated with success (and good moral behavior), and poverty is something ugly and that one brought upon oneself.
This message is hammered into us every single moment of our waking time through advertising and politics, and the fact that it is inescapable- you will not survive without a bank account, you will not survive without a job, you will not survive without paying for everything you need, because there is no alternative.
Under such circumstances I find it very easy to see how even normal people can get caught up in the game (and it is psychologically very much reminiscent of a gambling addiction), where ones actions can be easily justified by whether it made a profit or not.
Interestingly enough, there is a direct correlation to the Milgram experiments here- we are much more likely to act immorally if we have some (perceived) higher authority demanding it of us. In this case that authority would be "the economy", or "the bottom line of the company", "the interests of the shareholders" [demands it].