They knew that their nenderoids will replace the graduating Mumei. They knew they may get backlashed from hoomans for this.
To avoid this, they befriended Mumei by asking her to play OW2 with them out of nowhere. Just in time before Mumei's announcement
https://www.youtube.com/watch?v=5BrhQqDsVPY
Smart and hardworking, sasuga The new face of HoloEN!!!