Akame Ga Kill and the apolitical revolution

The world of Akame Ga Kill is one of the darker world to exist in fiction, if only due to the focus on the horrific nature of amoral and immoral aristocrats who exist disconnected from the masses they rule and their own humanity.

The plot of Akame Ga Kill is one of a splinter cell, dubbed Night Raid, aiming to overthrow the corrupt prime minister and hoping to liberate their kingdom, they lose allies constantly, in the end only 4 members of the group survive. The Kingdom is overthrown but replaced with another Kingdom.

The horror of the Kingdom can't be overstated, but the decision to continue a monarchial system in spite of that is one that begs the question, what's stopping the decay of the previous system.