It was more the fact that Saddam thought he could stay in power, exclude the UN inspectors and maintain the uncertainty of his arsenal. By backing him the war became much more probable and put Bush in a position, where he would have to back down after drawing a red line. That is something a country does only at high risk. When Saddam/Putin/Chirac/Schröder bluffed, Bush was forced to call it.
That, in fact, was inexcusable. The German people probably did not understand the consequences and thought Schröder was standing up for some sort of "Good". Schröder, though, knew all this and one must assume he acted willfully to increase the chances of war.