Constantine has long been an advocate of greater ecclesiastical authority, though in the past it's been a secondary concern to Allison's shenanigans. Constantine still sees himself as a theocrat on an extended missionary trip, which is why he still favors the theocratic system, though I don't know how many even remember his time in Astrum.
IMO the movement of power away from the theocracies is very much the doing of the theocracies themselves. In the past prominent theocrats, often rulers, were also very prominent Elders which prevented the council from acting against theocratic interests, allowing them to get away with the very things that would now earn condemnation (like Bustorsenzio harboring Bowie). The new generation of theocratic leaders however seem to have taken this for granted and shown little interest in church politics leading to the current situation of a nearly entirely non-theocratic Elders Council that has much to gain but little to lose in extending it's power over the theocracies. If the rulers of the theocracies take more interest in the church, perhaps even have their nobles vote in blocs during Consul elections, we could see quite a reversal in this trend.
