Constant war, etc might negate the ability to them. Lets face it when you go to war with a faction whats the first thing you do? Decimate their Fleet right? (if they have one) The ai doesnt do this very well. And is always at war with someone.

You on the other hand. You buy your time. Build your forces, ports, ships. The ai has one option and that is Conquer. Its not your fault or mine, its just the way it is. You cant expect AI to plan like you do. It is only a computer of course.