He was suing him for royalties, yeah. I don't think there's any foul play going on here, though. He was facing major knee surgery, which he openly explained how he didn't have the money to pay for it because he had no health insurance. I think that was probably the main impetus for the lawsuit.
Also, Bennett was by all accounts a heavy substance abuser for a long time (although he had been clean(er) these last few years). The drugs catch up with you in the end. In drug years, 45 is like 80 if you're regularly using them.