You can say it has always been about that, but for many, myself included, it’s about health and environmental impact first.

> if a vegan is on a desert island they'll eat animals to survive.

But that is only because there is no one else present to be able to tell that they are a vegan.

If there were a non-vegan person on the island, I am not sure the vegan person would eat animals.

This is honestly boomer humor that has long since expired. Sometimes people simply choose healthier options and tell no one.

IMHO, it's still a useful joke because one can immediately judge the joke teller to be worth zero of my time.