loki2371
Super Freak
You're thinking too much about logic. It was the minutiae of detail with which Lucas bogged down the PT.
Think of it as a Saturday morning serial. Ming the Merciless has destroyed a bunch of planets and only Flash Gordon and his close allies stand against him.
The Resistance was a separate force within the New Republic. The implication is that the nobody else has the stomach to put up a fight, or they just aren't ready to make a stand yet. It's a narrative device to tell a specific story, focussing on Leia.
Yeah you can look at it that way, but again Flash Gordon didn't span 40 years of a continued story through multiple mediums all interconnected (Movies, Animated series, Novels, Comic Books, and even (ugh) Video Games). It's still just lazy and bad story telling. No cohesiveness quickly takes the long time fan/follower quickly out of the story.
Also, we really don't know the true size of the FO's military forces. If Starkiller base is THE base of operations for the FO, and we saw the majority of their forces at the pep rally led by Hitler, I mean Hux in TFA, then they don't look too big. Not galaxy spanning at least. Just a small sized force with really powerful weapons. And knowing the New Republic has 100's of planets, even 25% of their forces that remained after disbanding the other 75%, would still likely out number the FO. The FO isn't large enough to attack every planet that's a member of the New Republic all at once. So it would take time. Time given to rally the other 75% of the army back to duty. All those ships, big and small, and soldiers are sitting somewhere in a state of decommission. I highly doubt they were dismantled for parts. The FO is still the serious under dog here.
The Empire ruled immediately, because the Emperor/Chancelor was already the head of the Old Republic. He didn't over throw the government through force. He defeated their 'Phantom" enemy in the Trade Federation, then simply assumed control after having been elected, and turned the "Republic" into the Empire. It happened over the span of years during the Clone Wars. Not in a matter of a day or two like Snoke's FO. Palpatine planned for years and years.