When people are comfortable themselves, they tend to be more kind, understanding, and altruistic.
I also suspect that this is also a long-term phenomena as opposed to the short-term implications featured in this study.
When growing up, I have seen those people become altruistic, helpful, and have more bandwidth for other people’s mistakes first who started earning comfortably first.
My theory is this- being socio-economically comfortable with peace in mind makes you more tolerant, altruistic, and kind overall.
Thus study mentions only "empathetic" people. But I think this goes beyond them.