⚪︎ Dismantling the Empire
After the ceasefire agreement, the New Republic absorbs the Empire's resources for peaceful purposes.
Dismantling the dictatorship.
However, even though the Emperor died, the Empire was not completely destroyed. The Empire's ideology was alive and they wanted revenge for overthrowing the Emperor. They thought dictatorship was better.
They were not able to effectively absorb the Empire's resources. Even though they were dismantled, it was surprisingly inefficient and mechanically processed.
This was a great opportunity to infiltrate a large number of Imperial agents into the New Republic. The agents slipped into numerous holes. Not all of the remnants of the Empire fled to the Unknown Regions, but rather "rehabilitated" and infiltrated the New Republic.
Later it became the First Order's intelligence network.
⚪︎ Subversive activities within the New Republic, peace created
They influenced the New Republic's policies from the shadows, making the New Republic weak in times of emergency and neglecting security. That's why their military is vulnerable.
Even if the New Republic realizes the true nature of the First Order, they cover it up within the New Republic. They steal information that is useful to the First Order and plant weaknesses in the New Republic.
They bring down inconvenient politicians, military personnel, and scientists.
They intentionally promote decentralization and democratization. During the Cold War, they intentionally prevent security crises and do not wake them up to emergencies. They do not let them realize that they are weak in emergencies.
They boldly promote the Empire's remorse. They celebrate the death of the Emperor. They make them adhere to disarmament, forget about the war, and enjoy peace. They make them believe that the Empire's revival is impossible.
On the other hand, there are no New Republic operatives in the First Order. The true nature of the First Order is unknown.
The longer the Cold War continues, the more the First Order can build up its military.
The New Republic was being manipulated from the shadows by the supposedly dead Emperor.
The New Republic government is a masterpiece built under the surface by the defeated Empire. On the surface, the Rebel Alliance has rebuilt democracy. After the Battle of Endor, they were certainly off guard.
They elected someone who was easier to control (than Mon Mothma) as Supreme Chancellor.
(The First Order has ample funds for sabotage)
The First Order was reluctant to run the country, so they also planned to make the New Republic bear the burden of running the country.
⚪︎Destruction of Starkiller
It would be over in an instant. It was easy to take hundreds of billions by surprise.
But many operatives would have to be sacrificed.