This is the one problem I've had trying to figure out in this series, the rest I've been able to explain to myself after weeks of research and wasting time.
I believe that this, along with explainations of what exactly the Dead Sea* is, would result from a clear ending. If Poore's militarism is because of Fiona's forest, or wanting to get it's hands on the Masamune or Sun Stone, we would have been able to see the beginnings of its military nature in CT, after we made those changes. The only changes we can't see are those after Crono and co. defeat Lavos, because the game ends. This would suggest that El Nido's discovery is the cause of Poore's militarism. As indicated in an interview with MK (not sure if I got that right...) there was an influence outside time that caused Poore's military build-up. This could be a number of choices. The two main ones I think have the greatest possibility of wanting Poore to build up it's military are FATE and Belthasar. FATE would because once Poore had discovered El Nido, FATE would want to prevent any major changes on the main continent that might prevent it from being built, and if it could spread its manipulation through Poore, and through Poore's dominance, the entire world, it could ensure its existance. However, FATE would probably be opposed to that idea as it majorly affects the future in a way that could possibly be harmful. Belthasar on the other hand, may have forseen Poore's military strength and conquest to somehow be useful to bring Serge to save Schala, since we already know how much else he's manipulated.
Either way, I believe that a more definite resolution would have revealed this as well as other questions like the formation of the Dead Sea. With Schala saved Project Kid is unneccessary and thus Chronopolis may never have had to been built (or at least travel through time). This would mean that FATE could not spread its influence through Poore as it isn't around. However, Schala says that now Serge can live his life, but this would neccessitate the create of the El Nido islands by Chronopolis (and then in would also appear to create the need for Serge to be saved from doom as he was twice in CC, unless perhaps Marbule did have a cure) and if FATE is still around then Poore's militarism would presumably be enforced. However if Belthasar organized the whole thing he could simply go back into time and erase the change once Serge saved Schala, allowing Guardia to flourish once again. Yet none of this is really explained in any detail in the game, I have a feeling that the developers purposefully left unanswered questions in the game in order for a sequel to more easily be fit in (CT really didn't have many loose plot strands and those it did have were turned into this convoluted plot).
*I say this because when visiting the Dead Sea they blame Serge for somehow causing it to happen, yet if Serge gets to live his life in the end of the game, wouldn't the future predicted in the Dead Sea still come to pass since Serge is alive?