I remember learning about this years ago. The olfactory sensors (bulbs?) are very close to the brain itself, but they’re separated from the brain by a layer of bone, which is part of the skull. If one’s head hits the steering wheel in a head-on collision, the shock can sever the short nerve fibers that pass through little tiny holes in that bony plate, disconnecting the olfactory bulbs from the brain. No more sense of smell, no more tasting food.
Some folks have genetic anomsia (no sense of smell) But excellent senses of taste......
I can’t smell anything, though I can sense changes in the textures of the air....however, food tastes great to me.