I think they’re saying if you start out that way naturally (like a peaceful sapient race on a peaceful planet) they’d be an easy resource for something less peaceful (it would just take one aggressive race to extinguish them). If peacefulness and powerfulness scale together during a species’s development, they may learn to learn strategies for peaceful coexistence before the stakes are too high for screwups.
I think they’re saying if you start out that way naturally (like a peaceful sapient race on a peaceful planet) they’d be an easy resource for something less peaceful (it would just take one aggressive race to extinguish them). If peacefulness and powerfulness scale together during a species’s development, they may learn to learn strategies for peaceful coexistence before the stakes are too high for screwups.