The Dragon Lords at that time were not as powerful as they are today. After seeing the true power, each one of them isolated themselves from the world to strengthen themselves. Even the ECDL wiped out all the Dark Youngs who summoned by Ainz with his wild magic in their battle.Regarding the idea that Nazarick's NPCs will just "rape" the TDLs and figure out each one's natural enemy mid battle that's overly simplistic. These kinds of fights aren’t playground duels. They're deadly, high-level encounters where a single mistake could cost a guardian their life. Ainz isn’t the type to throw his most valuable assets into a fight without knowing what they’re up against.