The majority of the Dragons of the Void fought to the death. They clung to the heels of the expeditionary fleet and tried to gnaw through as much flesh as possible before they perished. This diehard behavior was completely uncharacteristic of opportunistic pirates who only cared for money and their lives.
After the vanguard led by the Ark Horizon completed their firing pass, much of the pirate fleet lost their coordination. Every ship and every mech on their side ended up in random positions. They couldn't gather into a cohesive formation anymore that could withstand the concerted efforts of House Kaine.
Most of the other pirate gangs fled. They made for easy pickings and more than half of the pirates never made it very far before they got shot to pieces.
