WHY THE GENITALS

The perpetrators know that genitals are the most private and hidden place of the body. They know that their crimes will normally be invisible because the victim, out of shame, will keep a secret of the act. Only health complications lead a victim to talk about the ordeal. Many will hide the secret sometimes until it's too late and no help can be provided anymore.

REASONS FOR THE FEMICIDE

There is one obvious reason for this femicide : GREED.
The first step to quench that greed is to depopulate the region.
The D. R. Congo has too many natural resources, on and under the ground : a very rich biodiversity, lakes, rivers, a healthy weather and of course a lot of rare minerals. And the Kivu region of the Congo is one of the most resourceful in the country.
All those riches have always attracted disputes from foreign powers. The only people who have never fought for those riches are their owner : the Congolese themselves.
There have been schemes to plunder those resources over decades, even a century, but this one is to be the most evil and effective.

A DONE GENOCIDE
The Femicide is a done-ahead genocide.
If you sterilize women, you set up a nuclear-level bomb for a whole community but so silent that people may never realize what happened.
That is what the perpetrators of these crimes have resolved to.
With an average birth rate of 5 children per woman if you prevent her from having children by destroying her reproductive system, you have prevented 5 people from existing.
The number of offsprings that you have prevented from coming to life grows exponentially with time (5 x 5 x 5 . . .)

NO RECORD
The extermination has been well studied.
The first and principal target is usually the tribal chief of the village, called "Mwami", meaning King in local languages.
In communities or tribes, the Mwami is the person who "holds the records" of the inhabitants of the village. If there is no Mwami, the target is any administrative representative. The goal is to destroy all available records.
That makes the "switch" of the population easy, it will be hard over time to find someone who can name the true owners of the land or the original inhabitants.

RESULTS
By depopulating the area, these criminals now have a free hand to exploit all the minerals of the region without interference. They can repopulate the area themselves and why not later ask for the right to the land as local inhabitants.