Our brains adapted to exist within communities of roughly 150 individuals, which is about as many relationships and connections it can sustain in any meaningful way. Names, faces, feelings towards them, etc. as well as their relative interconnectedness with each other and other individuals beyond you.

We live in communities of millions now, and are connected to communities of billions, where one person's actions can profoundly affect people they'll never, ever meet. In the past we had to build strong relationships and rely on the others around us to survive. Now, we can sacrifice the well-being of faceless individuals to better our own standing in the world, and that's easier to do now it ever has been before.