Fairly simple, from my personal perspective:
God created all the different species of animals -— yes, every single one of them. They all lived happily together in Eden, because they all were herbivores there. There was incredible variety of interrelated and unrelated species. Then we humans got stupid. After we got kicked out of Eden, and death entered the world, one by one the species began to die off -— and it is still happening today.
Are you claiming that humans and trilobites existed coincidently?