In Horizon the catastrophic decision was to endow robots with the ability to draw energy from animal and plant matter, that's why they consumed all organic matt

In Horizon the catastrophic decision was to endow robots with the ability to draw energy from animal and plant matter, that's why they consumed all organic matter. Self-replicating nanobots alone wouldn't cause the end of the world. To end the world you really need something that can consume resources many times faster than the entire biosphere combined- without forgetting that the biosphere includes us.