Everyone there is a piece called the Insectoid Larva that appeared in 2 sets by the name INSECTOID, this means the buggoids might be Zotaxians/Insectoids, does anyone have an answer? or a reason why this piece has taken the name of an old theme?
The suffix -oid means "a likeness of" therefore Insectoid only means "Like an insect". When it comes to the old theme I would say it was more about their armor and vehicles looking like insects, whereas with Galaxy it's the creature itself which looks like an insect.
My theory is that the alien bug swarm was created by the Zotaxian "cruel leader" to take over holox and squash Gypsy Moth's rebellion, but they got out of control and started to try to take over the whole universe. Maybe they're mutated Bilgen bugs.