Man eats girlfriend's brain and heart.....

The junkyard analogy is interesting.
It also does not answer the question of where the parts cars came from in the first place.
One cannot make time the hero.
Given an infinite amount of time some things will never happen my accident.
Because beneficial changes will not be saved.
It has to happen right the first time or the organism (car) is doomed and the whole process has to be repeated.
That begs the question of why relative to the OP.
We don't know. It's easy to dismiss it as mental illness which it very well may be.
Like it or not, cannibalism has been traditionally practiced worldwide for "religious" reasons.
Metaphysical reasons anyway.
We can leave God out of it, but remember children, nature abhors a vacuum.