Because cultivating plant species preferentially is just like killing animals and people that feel fear and pain
Of course God can do anything he wants, if might makes right. Yet somehow we were made in God's image and we're concerned about preserving animal species that are going extinct, while God says, "Humans are really evil, the only way I can solve this is by killing everything that lives on the ground and in the air [and somehow the fish will survive despite living in water that is a mix of mud, corpses, freshwater and saltwater for a year]. That will show those stupid animals, I mean, humans." That apple fell pretty far from the tree.