Ask it to show you the list of kings and their ages and calculate the average yourself. I'll bet the answer is not 58 years. Regardless of the accuracy of the source data, ChatGPT is terrible at arithmetic. I asked the same question, and it told me the answer was 55 years.
I once asked ChatGPT how high a stack of floppy disks that holds 1TB would be. It returned 1.5 meters, which is clearly implausible to anyone who remembers how high a stack of floppy disks to install Windows 95 was. Obvs the model has improved over time as it now returns a more plausible 2.65 kM.
a. Until the 12th century or so, dates of birth even for kings are somewhat fuzzy, sometimes not even the year is certain. Deaths are usually better recorded, but anyway, there will be some systemic uncertainty there.
b. When evaluating whether a particular king's death was natural or not (the GP wanted to exclude non-natural deaths), we must take into account that a successful poisoning might look like sudden-onset gastritis or so, and that kings were absolutely a plausible target for such attacks. It works both ways; Ladislaus the Posthumous (died 1457) was widely suspected to have been poisoned, only a detailed scientific examination of his skeleton in the 1980s proved that cause of his death was a non-Hodgkin lymphoma.
I once asked ChatGPT how high a stack of floppy disks that holds 1TB would be. It returned 1.5 meters, which is clearly implausible to anyone who remembers how high a stack of floppy disks to install Windows 95 was. Obvs the model has improved over time as it now returns a more plausible 2.65 kM.