Sartar can be thought of a confederation of small cities centered on the large city of Boldhome, with a score of allied tribes, most of which have a say as to the running of one of the small cities. The Prince is the central ruler over all of this, with Boldhome as their palace.
When Kallyr became Prince in 1625, Sartar really was a mess. The city assemblies acclaimed leaders – city kings or rexes – upon their liberation from the Lunar Empire, with Kallyr ruling Boldhome and Swenstown and her ally Orngerin acclaimed as the ruler of Jonstown. Wilmskirk was practically autonomous. The city councils were responsible for day-to-day administration, drafting decrees, and advising on local policies.
After the failed Lightbringers Quest, Jonstown and Swenstown devolved to their city councils, and Kallyr delegated much authority to the Boldhome city council. When she was killed in early 1626, each of the cities were effectively autonomous, although they were certainly allies.
When Argrath became Prince in 1627, he quickly made it clear that he held supreme power over all the cities. He could and did intervene directly in city affairs, appoint officials, impose taxes, or demand military support. Decrees often required approval by the Prince, and major decisions were often dictated by the Prince. The city councils remained responsible for day-to-day communication, but Argrath maintained a mobile court that traveled with him on campaigns such as much of 1628-1632. Scribes, advisors, and treasurers issued decrees, managed finances, and communicated with city councils. The cities in turn coordinated with the tribes, made demands of military support, and provided financial resources. This combination of supreme power centered on the Prince with decentralized civic administration (often reinforced with Sartarite garrisons in Tarsh and later Saird), seems to have worked for Argrath, and the basic system appears to have been used throughout his long reign.
Were there any city councils that opposed, or were reluctant, to give up their power to Argrath? I’m sure there might have been individual people who were reluctant. But Argrath lit the flame and installed garrisons, and by that point it also was clearly him or collapse and conquest by the empire. He had the backing of the main cults and either the backing or the acceptance of the main tribes.