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.
The average birth rate in the Congo is 5 children per woman. If you manage to stop a woman from having children by destroying her reproductive system, then you have stopped an average of 5 people from existing.
The decaying of the community starts immediately because from those "preemptively" aborted children you can't calculate how many offsprings you have prevented from coming to life 20 years later and on.

NO RECORD
The extermination has been well studied.
The 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. And when there is no Mwami, the terrorists target any administrative representative to destroy all available records.
That makes the "switch" of the population easy, it will be hard to find 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 are repopulating the area themselves and will later on proclaim independance from the D. R. Congo through a formal referendum.