People have the incentive to not do evil and to do evil for money. When you abstract the evil away into 1 vote out of thousands then you abstract responsibility and everyone ends up in aggregate doing an inconsequential evil and it adds up to a big evil.
The tragedy of the commons.
That is to make a mistake of composition. An entity can have properties that none of its parts have. A cube made out of bricks is round, but none of the bricks are round. You might be evil, your cells aren't evil.
It's often the case that institutions are out of alignment with its members. It can even be the case that all participants of an organization are evil, but the system still functions well. (usually one of the arguments for markets, which is one such system). When creating an organization that is effectively the most basic task, how to structure it such that even when its individual members are up to no good, the functioning of the organization is improved.
Obviously because they don't give a shit.
The main thing here I think is anonymity through numbers and complexity. You and thousands of others just want to see the numbers go up. And that desire is what ultimately influences decisions like this.
If google stock dropped because of this then google wouldn't do it. But it is the actions of humans in aggregate that keeps it up.
Megacorporations are scapegoats when in actuality they are just a set of democratic rules. The corporation is just a window into the true nature of humanity.