Humans are really good at empathizing. But we are also really good at delineating between in and out groups. It was crucial to protect your tribe over every other human. We now have a massive problem of entire countries or even the world being the "in-group" since we have enough resources for everyone to survive.

But those people wanting power are really good at exploiting that group mentality to cause groups to form in people's minds. Then they use that delineation to withdrawn empathy from those new out groups. And when those delineations aren't coherent among actual groups, it causes a lot of divisions that can be exploited.