With the loss of the Emperor and Lord Vader, the Empire weakened rapidly.
Power was concentrated in the hands of one Emperor. There was no clear provision for the transfer of authority, so Governor Moff and others started a civil war and things got out of hand.
They were desperate to become an absolute second dictator, but the situation became chaotic.
It is very difficult to rebuild a system that has collapsed.
Then suddenly, Grand Admiral Thrawn, who was supposed to be dead, appeared.
He grasped the extremely complicated situation, but seemed surprised that the Emperor had really died.
Now that the risks of relying on one Emperor have been exposed throughout the galaxy, it was exactly as Thrawn had warned. The disadvantages of excessive centralization and structural flaws are revealed one after another.
This was the perfect opportunity to launch the First Order plan that Thrawn had been working on for many years.
Even though he was encouraged to become the second Emperor, he refused. This was a denial of centralization.
The construction of a system that does not rely on a single Emperor will suddenly become full-scale. The Empire's flaws are overcome one after another.
Power is distributed equally among the right number of staff members, and a flexible system is built.
This can calm the civil wars among the governors. It is much cheaper than rebuilding a centralized system.
Also, in order to lighten the bloated Empire, the civil war is used to cut down and streamline it.
However, Thrawn faces some unforeseen incident, and it seems that he will be usurped by Snoke.
The Sith Eternal behind the scenes have deemed Thrawn useless.
The First Order is built to function without a dictator, but in the end a weak dictator is installed. It's the best of both dictatorship and democratization.
I think Thrawn himself was probably manipulated by the Sith Eternal.
The First Order plan is worth using, but if Thrawn is not eventually overthrown, he will become a threat to the Emperor later.
(In reviving the Emperor, a system that did not rely on an absolute dictator had many advantages.)
The Emperor was interested in and praised the idea of a next-generation Empire without centralized control.
The Emperor was shocked to find that Thrawn was still alive, but realized that he must have had valuable ideas. Valuable ideas that he had developed in the Unknown Regions, after being excluded from the Galactic War.
The Emperor regretted having too much power, and acknowledged the drawbacks of centralization.
When he was alive, he was secretly fed up with the yes-man system. He was distracted by maintaining the system and neglected to formulate a genuine strategy.