I am not sure if what we read in the media was truly MJ's financial status. Remember, he was an easy target for leeches, so I think it would be a good strategy to "let them believe he's broke".
Edit ** After some research, I found out that If you are suing a person who is broke now, but is likely to be solvent in the future, it might be worth suing. Judgments can be collected for many years, almost indefinitely if you do the paperwork to keep renewing them, and they accrue interest as long as they are not paid. I think this was the case with MJ, those suing knew he would always make money from his catalogs, songs, etc.; don't know if that would be the case with Murray, though.