Throwing out some more ammo for discussion:

I think it begins with the Ancient's War Machines on Vland. Be bystanders for generations while the scary machines are slugging it out and you are TL 0 or TL 1. This is the origin of conservatism of the Vilani.
- Prior to the beginning of AotI, the 3rd Imperium has a Quarantine Fleet, separate and distinct from the Imperial Navy with presumably a mission statement similar to the Decider wafer's function.
- Not all existential threats in the novel were technological in nature. The two parasitic infestations are examples of this.
- Not all existential threats in the novel come from within an empire. The robots posing as organics chapter do not appear to come from within (I may be wrong there)
- The 3rd Imperium had to have Quarantine Fleet in the first place.
o: My God what kind of scary hellhole is Charted Space?

I think it begins with the Ancient's War Machines on Vland. Be bystanders for generations while the scary machines are slugging it out and you are TL 0 or TL 1. This is the origin of conservatism of the Vilani.