Unscrupulous is only one of the definitions.
Cunning and scheming are the other two. The Prince detailed how to gain and hold power.
It wasn’t a book that said immediately shoot everyone to solve all your problems.
So the original author was expecting violence in Godfather 2 but with more planning.
You gain and hold power by killing people you don’t like, look at any dictator that ever dictatored. 🙃