Basically, the motivation behind the Typhon Pact was that Bacco browbeat these nations into working together with their Federation rivals for the greater good, and it worked, and so they got to thinking, "Hey, this working-together-for-mutual-benefit thing works pretty well... but do we really
need to include the Federation? If it worked for them, why can't it work for us independently of them, and make us collectively strong enough that they can't push us around anymore?"