Sure, maybe it was in place in the 23rd century. Or just in 2301. Who knows?
Nevertheless, the assumption that the foundation of the Central Command coincided exactly
with the establishment of a military dictatorship ruling Cardassia is apparently a bad one. The Central Command was founded in the 19th century; a republic, in name if not in fact, existed in the 21st century. So unless the military was running a republic, it seems that Central Command didn't spring into existence ruling the Cardassian people.