Lions are obligate carnivores. They cannot be vegetarians, or at least, they should not be. They need taurine (amino acid found only in meat) for eye health, heart health and maintain healthy immune systems. They cannot manufacture taurine from other amino acids like people and dogs can. But they didn't know that back in 1936. A lot of cats went blind and died of heart failure 30/40 years ago because we didn't know how important taurine is to them. If you look at the ingredients of commercial cat food today, taurine is listed as a separate ingredient and most cat foods boast that they're grain free and the protein source is from meat.
Have you ever heard about the story Christian the Lion? Christian was a lion cub that was rescued from a department store back in the 60's by two friends in London. It's hard to believe that you could buy a lion cub in a department store back then. I remember the shoe store my mom took us to when we were little to buy shoes back in the '60s. It had monkey behind a glass enclosed cage. A monkey! All by itself. With no stimulation. And the cage was only about the size of a small closet. I feel sad for that poor little creature every time I think about it.
Anway, the two young men raised the cub by themselves until he started growing too big for them to handle. They then made arrangements for George Adamson to take Christian in at the Kora Nature Reserve in Kenya.
https://www.kenyasafari.com/christian-the-lion.html
I recommend checking out the video on youtube as well. It shows a lot of great video footage of Christian as a cub and his two 'dads'. You can clearly see how much he loved those two young men and how much they loved him too.
A lion called Christian The whole Documentary Full length
https://youtu.be/EZ-da0AZcRU