What you are missing is that Bison lived off whatever plants naturally grew in the land, and that their numbers declined and increased with the available food supply. The loss of natural habitat and biodiversity alone should be a cause for concern.
Of course it is wrong for factory farmed cattle raised in a shed, and for grain fed to cattle right before slaughter to change their meat, but I thought the bulk of their diet was basically unmanaged wild grasses?
Nowadays, most cattle lives confined in a pen, being fed grass and grains depending on the stage of growth. There’s still some very small farmers using the traditional methodology, but the vast majority of the meat you can buy in a supermarket - even fancy ones like Wholefoods - are the product of mass production.
The USDA’s website has a pretty good rundown of the process: https://www.ers.usda.gov/topics/animal-products/cattle-beef/...