Why did Germany want to become an empire ?
My first thought was delusions of grandeur.
After its disastrous World War I defeat and ensuing Versailles Treaty, Germany was impoverished and devastated. It's easy to see how the people voted for Adolf Hitler, who promised them riches from regaining its lost territory and eventually an empire -- the Third Reich. This mentally unstable dictator compared his visions of a German empire to the Roman Empire.