Okay, it it starting to come together now. It is a safe assumption that they are bad with money. Many people near or below the poverty line are bad with money. The social science of it is that they are so accustomed to living day to day that saving and planning ahead does not even enter their consciousness. So receiving a lump sum, without appropriate financial counseling, is going to result in exactly what you are seeing.
In addition, if the disability is depression/anxiety/some other mental condition, perhaps you assume he can work, but that is a struggle too. Perhaps he would only be able to qualify for minimum wage jobs. Being out of the market so long, with apparently no financial skills and poor health, I would also guess his qualifications are not stellar. Given his mental condition, perhaps he cannot hold even menial jobs for very long. Getting motivated to apply for more minimum wage jobs that are not going to pay much more than your $1k/month disability check, only to go thru the process over and over, is tough. So he stays home, mismanages the little money that he does have, and sinks further into depression. I've seen it happen many times. Sometimes mental illness looks like laziness, but it is no less crippling than the more obvious physical disabilities.
Should this guy be doing more? Absolutely. Does he need help beyond what he is already getting? Probably. Is life fair? No. Is he gaming the system? Maybe, maybe not. Maybe he just doesn't have any legitimate options.