Even though land holdings were considered the primary cause of the thirty years’ war, the war was actually over

The Thirty Year's War was over religious disputes. It started when Holy Roman Emperor Ferdinand II of Bohemia tried to limit the religious activities of his servants, igniting rebellion among Protestants. The war draws closer to involve the major powers of Europe, side to side with Sweden, France, Spain, and Austria.

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.

“what were the main causes for the decline of the roman empire? ”