"Unprovoked" in the sense that no one had started shooting yet. Though what caused the buffalo to randomly charge directly at and over some guy dressed like a hunter, I guess we'll never know. Certainly seems like a major fuck up on someone's part.
As for the "conservation" thing yeah, it's bullshit on top of stolen valor. There's some hunters, poor folks, who rely on the land and so do develop a more conservationist approach to the idea that the habitats they require to live must be protected. And for deer hunters, because ranchers killed off all the wolves, deer do need predators to thin populations or else they over stress their habitat and start dying from shit like CWD. So its a human made problem but human hunters are one solution.
But big game hunters are rich folks that pay real hunters to show them around and then proclaim themselves to be environmentalists for assisted poaching of endangered species. They rely on those other things I said to provide moral cover for their gross hobby. Fuck big game hunters.