I feel sorry for him simply because he did try to do the right thing initially. All the big mistakes he made, he made after he got back on drugs and I doubt if he would have relapsed again had it not been for his wife. After she started using again he sent her to rehab a couple of times. When it was clear that she wasn't going to get her act together, he kicked her out. He didn't want the drugs around him, since he was an ex addict, and he didn't want the drugs around his daughter. I think up to that point, he had his head in the right place.
The turning point was when she begged him to take her back. He did and that was the beginning of the end, because when she started using again, this time he started using with her. And that's when he hooked up with that new shady advisor who had him make a bunch of crappy investments and purchases. He and the wife were always high and the daughter had to call the cops on them a bunch of times.
I think whenever an addict or an ex-addict wins the lottery, the result is always the same. They go back to using and they blow all their money on drugs. But the reason I have sympathy for David is because it appears he tried really hard not to slide. Between putting the wife in rehab and then kicking her out, he made an effort to stay on the right path. I don't think Jack Whitaker ever put his granddaughter in rehab or put his foot down to get her to stop. And that's why I find it ironic that David died alone and broke, in part because of his wife, and that the wife moved on to husband #2 and got on with her life. Go figure.