So Saul was evil huh? I'll bet modern day evil leaders like Saddam Hussein and Mahmood Ahmadinejad would get along with him just fine!
If you had taken the time to actually read the Scriptural account of the kings of Israel several things would jump out at you:
(1) The prophet Samuel warned the Israelites in the name of God that having absolute political rulers would be a grave danger to Israel.
(2) Saul was corrupted by the power, did evil things like undermine Israel's defensive strategy, partake in revenge killings and unjustly punish rivals in order to aggrandize himself.
(2) David, although a better man than Saul, was also corrupted by power and did evil things, was severely punished and had to beg for forgiveness for his sins.
(3) David's heir Solomon, despite his great intelligence and administrative and political acumen, was also corrupted by power and was led astray.
(4) The lust for power among Solomon's descendants broke the people of Israel into two warring camps and initiated a period of decline and hardship, leading ultimately to the utter destruction of one of the warring camps and the captivity and bondage of the other.
The entire history of the Israelite kingship as narrated in the Bible is very critical of the institution of kingship itself and the attitudes and behavior that absolute political power engenders.
To return to your earlier point about Islam not being a political ideology I will point out that in Judaism the very notion of absolute political power is considered suspect, an enormous temptation to sin and a presumption against God.
i will point out further that in Christianity's New Testament Jesus goes out of his way to emphasize humility and service as preferable to power and wealth and St. Paul specifically commands Christians to live obediently as citizens of their existing government rather than use violence to seize power. The main political question of Christian Europe from 800 AD to 1600 AD was how much authority a king is allowed to have over his subjects and how much influence the Church was permitted to have in political matters. For the medieval Christian it was a truly pressing question with no obvious or easy answer.
However, in Islam, it is a simple question.
The Caliph is the supreme political and religious entity. He has complete power of life and death over everyone living in the ummah. Every Muslim is required by his religion to contribute to jihad - i.e. the struggle to subject every living person and every square inch of territory in the world to the power of the Islamic Caliph.
In Judaism and Christianity the relationship between politics and religion is a complicated question that is constantly debated.
In Islam politics and religion are identical.