What is the importance of separation of powers in a political system?
user
The importance of the separation of powers in a political system can be observed in how well implementations of Trias politica function.
in Trias politica which is the most well successful implementation of separation of powers. you notice that the powers keep each other in check. With Police, Judge and Politicians being the three powers.
This will not prevent bad descisions but more likely will prevent extremely bad decisions and extremely good decisions. and will keep decisions more moderate. 
Mustafa Kemal Atatürk was a well known dictator that implemented some great ideas while Adolf Hitler implemented some horrible ones.
If powers are separated you will have less extreme cases that is the Importance of separation of powers
assistant