Complex sentence: Grosche was arrested for a year by the Nazi government on the grounds of being a Socialist, and his connection to Aleister Crowley was cited by the Gestapo as the main reason for his detainment.
Split into simpler sentences: Grosche was arrested for a year by the Nazi government on the grounds of being a Socialist. Curiously enough, his connection to Aleister Crowley was cited by the Gestapo as the main reason for his detainment.