Medieval mindset in Nigeria - Cui bono?

Details are beginning to emerge from attacks Sunday on four villages in central Nigeria, where witnesses say members of the predominantly ---- ---- ethnic group targeted villages that were home to members of the mostly ---- ---- ethnic group. On Monday, local officials counted 378 bodies...

The weekend's attack appeared to be a reprisal for violence that claimed at least 300 lives in January, when ---- villagers targeted ---- in a separate, nearby village...

At a mass burial... angry residents talked of revenge as they gathered around a large pit and scattered dirt on several dozen charred and bloodied bodies...

An elderly woman prayed at the edge of the burial pit, chanting. "By God's grace we will enter their villages and kill their women and children," she repeated.

"We will do much worse to them," one man said.

I would assume the hatred goes well beyond religion per se to involve economics, land, food and other basic needs stretching back for generations.  I've redacted the identities of the religious/ethnic groups involved in this specific incident, because it really doesn't matter who started what first.

One has to wonder who ultimately benefits from violence such as this.  It's probably no coincidence that it's occurring in one of the countries blessed (?cursed) with abundant oil reserves.  Someone behind the scenes is stirring the pot for their own monetary/strategic benefit.

Cui bono?