He also had congestive heart failure and his arteries were 30-40% blocked a year before his death. After he fell, he died during surgery to remove a blood clot in his brain. It's hard to say conclusively what caused his fall and ultimately his death, but we do know for a fact that he had heart problems.

I don't believe this matters either way, though. You shouldn't be basing your understanding of what a healthy diet looks like on the outcome for one individual. Experts in the field of human health do not believe that Atkins' diet was healthy, and that should suffice (though of course there are plenty of other unhealthy diets, some of which have problems that Atkins avoids).