They did it in book two, Player of Games. They destroyed the Empire of Azad because they considered it a distant ideological threat.

I never got the impression they thought Azad could ever be any sort of threat. They destroyed the power structure because it was horrifically abusive.

Yes, biggest minds in the galaxy and their best idea is to run the George Bush playbook. What was the aftermath of destroying the governance of such an advanced civilization? Did millions die in civil wars and famine afterward or did they stick around for decades doing nation building and spreading freedom with autonomous attack drones?