https://amp.theguardian.com/lifeandstyle/2023/sep/13/cats-may-get-health-benefits-from-vegan-diet-study-suggests Cat owners who fed their cats a vegan diet likely self reported healthier pets because they're not taking them to the vets to find out if anything is wrong. If they did, they would know that cats are obligate carnivores who easily get nutritional deficiencies without meat.
An article about this from an actual veterinarian: https://theconversation.com/is-it-really-safe-to-feed-your-cat-a-vegan-diet-213356