With regards to a financial motive, there's a lack of information that causes me to go in circles. Missing for me is, the source of money in the family, and the need to know more about BM.
At a superficial go at it, it's tempting to say "he was about to lose his money tree, and wasn't going to stand for it". Certainly possible.
Thing is, we don't know the source of their money. It could be that BM was, and this is where a person would need to know more about BM. Some people just know how to make money. If they lose everything, they know how to make it again. Many here have pointed out arrogance in BM. How arrogant? If it's to the point that he's not worried about making money regardless of the current situation, financial motive becomes less. If he was about to lose half or more of what he had, that sure would be a pain, but how much of a pain? Could have been a nothing burger to him.
This leads me think that it at least possible that money was not that much of a motive. MOO.