Why not dead animals?
A diet consisting of exclusively animal products does not result in the ability to do high calorie per hour exercise for long periods of time due to absense of sufficient carbohydrate
If one is then going to eat at least some plant products to get sufficient carbohydrate then one might like to get some of their protein from plant sources
Also they are giving animals mRNA vaccines which would potentially result in animal products having a different chemical conposition
So not protein but carbohydrates with the added context of it's for exercise.
And not complete proteins.
So meat and potatoes.
I literally eat beef and giant smarties and lift weights and go on treadmill runs for a couple of hours.
Also I have not had good results eating corn or beans for protein because they would make me feel to full before I got enough protein. But pea protein isolate does not make me feel too full. There is an exception in that I found refried bean burritos to be a good source of protein if combined with beef tacos or chicken burritos at taco bell, but generally if I just had canned beans combined with some sort of grain it would make me feel too full to get enough protein.