Goldfish are a species of carp, and as such, have similar predatory behavior in the presence on non-carp species. They aggressively compete for the available food, and their presence drives out other native species.
Invasive species are a problem everywhere, not just in Colorado, and it takes a while to establish a new equilibrium in the ecosystem that has been disturbed. Just look at the various invasive species that have escaped into the wild in the Florida Everglades, even the presence of alligators cannot keep them under control. Ball Pythons will even attack and consume young alligators. No match, though, for an adult bull alligator.
I had a job estimating repair costs to railroad that got wiped out in the flooding in Lyons, CO a couple years back... Somewhere I have pictures of a few HUGE rotting Carp carcasses that were left behind when the floodwaters subsided. HUGE.
What would happen if they dumped a bunch of large mouth bass in the lake?