He died in 1973 in Bournemouth, England.
The simplest answer is that J. R. R. Tolkien died because he was an 81 year old human being. Tolkien died on September 2, 1973, of pneumonia. It's also important to note that he died 21 months after...
He died of old age. He was 81.
J.R.R. tolkien's wife died at November 29, 1971
2 September 1973, at the age of 81