God works on a mind-bogglingly immense scale. Earth is but the tiniest spec in the cosmos. God likes variety. Consider the bewildering variety of fishes in a coral reef. God is cruel, or is for some reason is unwilling or incapable of combating cruelty.
Animals kill each other.
Billions of animals every year suffer and die of overcrowding, starvation or dehydration. Humans do the most hideous things to each other and God almost never intervenes. God is not at your beck and call to perform miracles for you, unless you happen to be a saint. God seems to run the universe, nearly always, by rigid mathematical rules. God is no prude.