You're forgetting self-replicating colony ships.

Factories can already self-replicate given human help. They'll probably be able to do it on their own inside the next two decades. After that, we're looking at self-replicating swarms of drones that tend to become smaller and smaller, and eventually they'll fit on a spaceship and spread across the galaxy like a fungus, eating planets to make more drones.

That doesn't strictly require AGI, but AGI would have no discernible reason not to do that, and this has evidently not happened because we're here on this uneaten planet.