You write that you haven't seen major news outlets focusing on questions like "How did Epstein make his money? Who were his clients?"
Here are some major news outlets which have tried. None have succeeded.
New York Magazine - http://nymag.com/intelligencer/2019/07/how-did-jeffrey-epste... - "How Jeffrey Epstein Made His Money: Four Wild Theories"
Vanity Fair back in 2003 trying to figure out the mystery - https://www.vanityfair.com/news/2003/03/jeffrey-epstein-2003...
Business Insider - https://www.businessinsider.com/how-financier-jeffrey-epstei...
Bloomberg - https://www.bloomberg.com/news/articles/2019-07-08/the-myste...
You ask "What did his business associates know about the sexual allegations?"
The only known business associate is Wexner. He has declined to comment, says Bloomberg.
You ask "Who does Acosta claim told him?" He has declined to comment. Eg, the Miami Herald at https://www.miamiherald.com/news/local/article220097825.html says "Acosta did not respond to numerous requests for an interview or answer queries through email."
"The simple explanation" is that it was hidden well, protected by powerful people, and had not yet been figured out.
I have no doubt that "the answers would reflect badly on people who have power over them". That's how it has been squelched or diminished until now.
Other than the one comment, is there any evidence that an intelligence agency is really involved? Why can't it be a bunch of sexually abusive plutocrats supporting each other with their connections of power? Why can't the reference to "intelligence" be a convenient cover?
If it were the CIA or Mossad, do you not think that, perhaps, some time in the last 20 years they might have told him to tone down as he's going to get caught, and destroy their decades-long effort?
What are the connections between Mossad and Acosta? Any Epstein connections wouldn't affect the federal prosecutors' office, yet it was they who gave Epstein such lenient terms.
If Julie Brown, the investigative reporter who worked on the story for a long time for the Miami Herald, had been able to figure out any of these questions, do you think she would have reported it?