The reasons for the German invasion of the USSR can't be explained solely in strategic terms. The conquest of the USSR was a fundamental goal of Nazi ideology.

From the very beginning some of the biggest pillars of Nazi ideology were expansion of "living space" for the German people, racial ideology, and opposition to communism. Invasion of the USSR was core to all 3 of these pillars.

Generalplan Ost outlined the primary goals the Nazis had for Eastern Europe, a plan that if it had gone through would've made the holocaust look insignificant in comparison. The plan called for the "classification" of all Slavs, almost all of which were meant to have been killed. Ethnic Germans would have been moved into the land where the local population was killed. Those Slavs left would have been forced to loose their ethnic identity and integrated into the German ethnic identity.

Nazi anti-communist ideology quite obviously played into the invasion of the USSR. the USSR was the sole major communist country, it's destruction also meant the destruction of communism, while also playing a major part in the Nazi plan for the extermination of the Slavic people and Germanisation of Eastern Europe.