This story is really just tragic, but it does reflect a reality in the California prison system. Very few people on death row die by execution. The leading cause of death is old age.
George Smithey, for example, was 70, and had been on Death Row since 1989. That's 21 years, during which the state has spent a fortune on high-security imprisonment and legal appeals. It costs millions to prosecute the death penalty to its conclusion, and in most cases, the state has to pay millions more to defend the accused. Those costs are mandatory; the Supreme Court (and the basic rules of human civilization) require that someone facing the ultimate penalty be given every possible avenue of appeal, every chance to make sure that the state isn't making an irreversible mistake.
Life without parole is way cheaper -- and in most cases, gets you to the same place anyway.