So… why were they fighting? (Ch 13 spoilers)

Something I still don't get. Maybe I missed something but if Void commands the Ghosts and also created and commands the Ganglion to the point he was personally leading them during the attack on Earth... why the big battle? Why are they engaged in a giant brew-ha-ha in Earth orbit instead of attacking in unison? Is he stupid?

I get there's this whole spiel about observing rhe srruggle for life and the bested will be erased blah blah blah but.. I don't know.. pock a better time for that like when you're not actively trying to steal the Ares? I mean it's already rather disappointing they dropped the whole idea of an intergalactic war between thr Samaar Federation and the Ghosts but I have a hard time making sense of this bit.