When the Zergs attacked the civilizations of Order from the edge of the Star Ruins, most of the civilizations of Order in the entire universe were still in the civil war stage. No one cared about a group of insignificant bugs.
When the first universe that was invaded fell, the Zergs finally revealed their ferocious fangs in front of the universe of Order.
They occupied that universe and used it as a hatchery.
All the energy that could be devoured and digested was swallowed into their stomachs for reproduction, whether it was land, population, creatures... As long as it was something that could be digested, it would be hunted as food.
Such a race that was filled with destructive and destructive characteristics naturally attracted the condemnation of other races. The surrounding universe was filled with armies, and the Zerg had experienced a period of defeat by other races.