The Cat’s whiskers? Well a varied diet is the best for longevity it seems.
I think a lot is genes and luck. I’ve seen so many cat people who have spent so much helping cats with chronic conditions live fairly normal lifespans. Many of those conditions have nothing to do with diet although often changes can help enormously in controlling them. The lifespan of domestic cats has increased mostly because they would often be put down at the first sign of serious illness whereas now those conditions can be controlled or even cured, but as with people not everyone will make it to their 90s or beyond. and not everyone who gets to be that old has lived perfectly or purrfectly.