Mo

They believe it was Arnold van den Bergh

While there are multiple theories, the latest one was about another influential Jewish business man, apparently with connections in the nazi party, whom to safe himself and his family from being sent to the camps disclosed the hiding places of Jewish people. What is not clear from that latest investigation is if the man’s disclosure referred specifically to the Franks family, OR, if he just informed about possible places of hiding but in a more anonymous way.

I'm not sure your point about "knowing about the Annex", but I think the lady in the video explains it quite well. Coming in from the front, you cannot see the back of the building, so you don't get a perspective on how deep the building is, or how far back it goes. Amsterdam is a big city, and this building was one of many, many buildings and didn't stand out in any way. Fresh air? They could open the windows at night. People noticing the workers? That was their place of work, so it was completely normal that they would be there. As-Salamu Alaikum

You're talking about Roger Garaudy the Holocaust denier and anti-Zionist? Convicted criminal and antisemite. He wasn't an expert on any of this, he just hated Jews. Oh, and he was also crazy. As-Salamu Alaikum.