Human behavior is remarkably different depending on whether or not I'm the sole person on stage responsible for an action or whether I'm a single anonymous vote.
This is exactly it. In a large organization, everyone can mentally offload any responsibility to someone else.
The rank and file can say "It's not my decision, the execs told me to do this".
The executives can say, "It's the board pushing me to do xyz and if I don't do it then someone else will, so I might as well just keep my job".
And the board can say, "Well, we just told the execs to maximize shareholder value, we didn't tell them to do anything unethical."
So you end up with a situation where no one feels like they bear any responsibility for the actions of an enterprise and you have a group of individuals who, as individuals, are moral but are contributing to an organization that is acting immorally in the aggregate.
I would argue that the individuals are immoral and the corporations foster conditions that reveal this fundamental immorality that is usually hidden. We only act moral if there's a consequence detrimental to ourselves.
Hence people act immorally in the name of survival.