The Tatchwower (oops! don't drink and post, kiddies) used to love to point out the seeming illogic of whales and tortoises vastly outliving humans.
What the heck! I used to wonder about this too. The answer might be simple: we got here by evolution and it doesn't give a rat's a$$ about us. Those long-lived animals got lucky enough to have adapted to oxygen deprivation and that may have had a big effect on their longevity.
I think this paper provides a strong hypothesis about animals that fail to age at all !