Many times an injury or illness doesn't show up immediately. You can only imagine what Mr. Lawton has suffered.
Who are you to judge him? In order to get his disability rating he had to prove to the VA beyond a shadow of a doubt that his disabilty was and is service connected. And it isn't an easy process.
How do you know that I don't know? Back to the basic premise of how you complete 24 additional years in the Army if disabled to that extent? Also didn't see what the degree of disability was.