Why does so much inter-factional conflict focus on issues of inequality?

Because complaining about "inequality" is currently high status.

Throughout much of recorded human history there were almost no complaints about inequality even though inequality was much worse then.

I also find it amusing how all the people, who normally complain that evolutionary psychologists don't take into account cultural differences, are offering gushing praise when confronted with ev-psych of which that is actually an accurate criticism.