What is an explanation of "Crow Tyrannosaurus" by Ted Hughes?

Crow Tyrannosaurus is a poem about life, death, and the need to kill in order to survive. The crow sits in a tree and watches as other creatures around it eat each other. First, a swift—a kind of bird—flies by, and the crow notices that it has eaten insects. Then a cat eats the bird, a dog eats the cat, and finally, a man walks by and is described as

a walkingAbattoirOf innocents—His brain incinerating their outcry.

The crow sees all of this and wonders to itself if it should become the good, or "light," in the world by ceasing to eat. But then it sees a grub, and, acting on instinct, the crow eats it and many more.
This poem looks at life and death and comments on the necessity of death for the survival of other creatures. Interestingly, though, the poet makes the main character a crow and gives the crow the thoughts about the cruelty of death and the desire to change.
The fact that the crow cannot change its nature may suggest that resisting the natural order of things is futile, and while we may be aware of the issues, we are powerless to stop them. Or it could be the poet's way of challenging that notion, almost like reverse psychology.
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