As someone who volunteered in a museum right near the Newseum, their biggest problem was the competition. The Smithsonian and the National Gallery of Art being some of the best museums in the world, right across the street, with much better stuff and totally free was always going to be hard to compete with. The only private museum that has managed to survive is the International Spy Museum, which went all in on fun and interactives, and much less on education, and has a lot less prestigious footprint.