Why had the Franks settled in Holland? - They thought it was more safe from invasion.
Were the Franks wealthy? - Yes. The family owned a bank, which explained many of the photographs that only the wealthy could afford at the time.
Was their hiding place secret? - Well, their protectors, their protectors' associates, and their vegetable suppliers knew. Their whereabouts were revealed when the tide of option changed.
Why did the Frank family never go out? - They were afraid that the Germans would capture them, and they looked "too Jewish" since they didn't obtain false identity paper, like most other Jewish people.