WRT historical populations of gray wolves: 200 years back there was a lot more lightly-populated territory in the western US. Aside from the bison, the early European travelers commented on the numbers of deer, elk and antelope.
So, we changed all manner of balances of various populations, both animal and human. Absent livestock, there are fewer animals to support a large population of predators--whether it be bears, wolves or cougars.
Seems to me that it won't take all that many wolves to have a population whose demand for food strongly degrades the available supply. IOW, there is a serious need for control of their numbers.
Obviously, some folks feel that "zero" is an appropriate number.
Another "numbers" problem, I guess, would be that of coyotes. As the wolf population declined, the coyote population increased because of reduced competition for food. We still have this larger population of coyotes, and now we add wolves into the equation.