As a young man, Von Stauffenberg's political views were heavily influenced by his membership in a literary circle headed by the poet Stefan George. The circle led him to a rather poetic image of a grander, finer Germany that would emerge from the chaos of the Weimar republic.

When Hitler rose to challenge Hindenburg for leadership of the country, von Stauffenberg at first welcomed the change, thinking Hitler would be the man to reestablish order and bring Germany to its proper leadership role among the world's nations.

But as time went on, Hitler and the Nazis seemed less and less noble. Von Stauffenberg did not approve of the various anti-Jewish measures before the war. Just how much he sympathized with the Jews for their hardships is not entirely clear, but there is a definite sense he felt these measures diminished Germany in the eyes of the world, convincing other nations that Germany was not the proper leader of the world but rather a bunch of vicious barbarians.

When stationed in Poland von Stauffenberg became familiar with various atrocities that made him even more unhappy. He didn't like Poles, but he felt some officers were going too far, particularly SS.

It was the invasion of Russia that completed his disillusionment. Von Stauffenberg was a capable officer thoroughly experienced in issues of supply and logistics, and it rapidly became apparent to him that the Eastern front was a quagmire that would result in a pyrrhic victory at best. Hitler started interfering in military decisions more and more, and it seemed his interference just made things worse.

Furthermore, he became aware of the activities of the Einsatzgruppen, the SS murder squads that were shooting whole Jewish communities after they were passed by the German lines.

At this point von Staffenberg decided Hitler needed to go, though it would be some time before he would be contacted by the resistance group that could actually support him in a realistic plan to get rid of Hitler.

By no means was von Stauffenberg much motivated by personal gain. It seems von Stauffenberg was a romantic at heart, a man who needed a cause to follow. For a while, Hitler seemed to lead that cause, but when Hitler failed him the cause became to get rid of Hitler.

My source for the above is Danny Orbach's book The Plots Against Hitler.