Why do people kill each other over religion?

I find it ridicules that there is entire wars fought over religion, it seems like a waste of resources and human lives. There has been "Holy wars" for 1000s of years, people fighting in the name of their God. The most recent Holy wars are in the east and the US wastes billions of its dollars to send marines to the east just to protect are interest (Oil, and other resources).Why must people fight about their religions? Why cant they just get along because by definition the Muslims, the Christean, the Catholics,and the victimized Jews all worship the same guy God. The only difference is i believe the Muslims have a different name for him and all these religions have a different way to worship him, but when it all boils down they all worship the same God. So why waste all this time fighting about God its such a pointless fight and gets the human race no were. Course i understand the reason of a religion it is to calm the person about death they want to believe that when they die they will have some were to go, most common name for this place is heaven. But why bring death to you faster or faster to others? I cant blame religion for all the wars because the greedy people that run are nations don't give a flying hoot about us or the future just their own interest.