This link may answer some of your questions from Anne Frank Remembered.
http://www.ushmm.org/education/foreducators/question/

COMMON QUESTIONS ABOUT THE HOLOCAUST

• How could Hitler make the Holocaust happen by himself?
• Why didn’t they all leave?
• Why wasn’t there more resistance?
• How did they know who was Jewish?
• What happened if you disobeyed an order to participate?
• Wasn’t one of Hitler’s relatives Jewish?
• Why were the Jews singled out for extermination?
• What did the United States know and do?