It could be that the cage is twisted so the lower pulley is out of plane with the chain coming to it from the bottom of the chainring. Understand that there's normally some of this since the RD moves in and out so the pulley can' line up with every chainring.
The other possibility is that the pulley is worn, and the chain coming from a normal angle is running up over the side.
Do some eyeball gauging sighting down the chain like a rifle, and check the condition of the lower pulley.
In any case I doubt it's the hanger which seems to have the RD hanging straight up and down, and for the chain to derail to the inside of the lower pulley it would mean that the lower pulley is outside of the chainrings, not bent inward.
So twisted cage, or worn lower pulley, or some combination of both are more likely, though it is possible for the hanger to be twisted.
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