Hey Joe,
To my knowledge there were a few people that did try to intervene to help Jaco. Some very well known bass players too. Some of whom I've interviewed and or studied with. The problem lies with the people that tried to sponge off of Jaco and always bailed him out just to get what THEY wanted out of him and when they were done with him, basically left him to his own demise.
Sure Jaco had a very serious medical problem, no question about it and with today's medical advancements, may still be alive today. From what I've read and heard though, Jaco would still be alive today if more of his so called friends were more interested in Jaco the human being as opposed to Jaco the bank roll.
Like Rami, I've read his daughter's letter and it will bring a tear to your eye. I've also read the Jaco book, I think it was Bill Milkowski that wrote it. Pretty informative but I think it was a bit one way as well. Anyway, I just wanted to comment because I know there were people that did try to intervene however, there were also people involved in his life that shouldn't have been.
Peace,
Dino