what crops that are fed to beef chicken and pork are parts of plants that people won't eat for the most part. The same fields that grow the soybeans we use for oil are growing soybeans that are used as feed. The same soybeans that are used for oil are used for feed.
This is sometimes true. However, e.g., about 4% of the farmland in California is used for alfafa, which is just for livestock. Alfafa is also a very water intensive crop.
Additionally, there are other uses that livestock corn feed could be put to if there weren't so many damn cows, so it's not like we'd be throwing away megatons of silage if it weren't for cattle.
but beef, chicken, and pork continue to be made in increasing amounts. things are getting worse despite the fact that vegans exist. being vegan doesn't help the planet at all.