O'Reilly's whole deal is that he doesn't believe that the order of the universe as it stands, which perfectly supports life, and humans, and only takes place on Earth and not anywhere else on Mars, could be the result of just random chance.
By asking how did it get there? He's also implicitly asking "Why". Clear as day. Why did sometime this world form from nothing and build a landmass so perfectly adaptable to humankind? Why did, this random collection of molecules and energy form into microorganisms that would develop into beings capable of logical thought? Etc.
O'Reilly is questioning how a 1/10000000 twist of fate that led to this universe developed into what it is today without an overseer or intelligent design.
Well we formed under this planets conditions, not the other way around. From what we know about the formation of this planet all things required for life were present. Life on this planet under these conditions was very probable looking from a recent point in time before life formed here. Life should not be on mars currently, its not suitable for life like the earth is.
Well Bill believes the universe came from nothing as be believe god said it and poof from nothing sprang forth the universe. No intelligent atheist would ever say something comes from nothing, that is nonsense and not possible with what we know about the universe.
Also, look at the evolution of man. We evolved to best adapt to the terrain, not the other way around. The planet was not built for us, but us for it.