Okay. I'll try to condense it.
2 million acres were originally set aside by U.S. Grant. In 1903, when TR visited, the park was teeming with game. The Park Service was formed (by TR). This bureaucracy's sole job was to maintain the park in it's original condition.
Within 10 years the landscape TR had seen was gone forever. Park managers had taken a series of steps to maintain and preserve the park:
Early managers believed that elk was going extinct. They eliminated predators. They shot and poisoned all the wolves in the park. They forbid Native Americans from hunting in the park. The elk population exploded, they ate so many of certain trees and grasses that the area began to change. Beavers vanished because the trees they used vanished. When beavers vanished meadows dried up, which led to changes in the trout numbers and the otters left. Erosion changed and marred the landscape, forever. By the 20's the managers realized that the elk population was too large and unsustainable, so they shot them by the 1000s. But, the early mix of trees and grasses did not return.
Studies have revealed that Native Americans influenced the park in a variety of ways. Keeping the numbers of elk, bison and moose in check. Native Americans also managed the area thru control burns, control of the forests and thinning herds.
Grizzlies were initially protected, then killed off. Wolves were re-introduced. Field studies of animals using radio collars were started and ended, then resumed again on endangered species.
Fire prevention efforts were implemented, which led to some deforestation (we have learned since that some trees need fire to reproduce), and when 'controlled burns' were re-implemented, some areas burned so hotly that the ground was sterilized. This required re-seeding.
Rainbow trout were introduced in the 1970's which killed off native cutthroat species.
As noted, disastrously intrusive intervention, followed by attempts to repair the intervention, followed by attempts to repair the damage caused by the repairs. One mistake after another.
I hope this helps and explains my comments above. As soon as the volcano there explodes, then it will all be altered again, by Mother Nature.