It don't think the mystery is so great. Lett explained it in simple terms: "we have more money going out than we have coming in brothers". In that situation you need to sell assets and cut costs to survive financially. It's not a question of "what are they going to do with all the money". The cutbacks and begging for donations are all about keeping afloat.
In many ways it's been a long time coming. They've been living on borrowed time since they stopped charging for literature in the 1990s. The displacement of print media, the crash of 2008, the abuse claims, declining recruitment, and aging staff have all exacerbated the problem.
What will they do when they run out of assets to sell? Can they cut costs enough to make the religion sustainable long term?