A sceptic might argue: if God created the universe as a special place for humanity, then surely he made it vastly bigger than it needed to be. What a colossal waste of space and energy.
There are something like 200 billion galaxies in the universe each containing, on average, about 200 billion stars. But if the universe were much less massive than this then the early cosmos would never have been capable of producing by nuclear fusion elements heavier than helium (elements like carbon, nitrogen, oxygen and so on that are necessary for physical life). Conversely, a much bigger universe would produce elements as heavy as, or more heavy than, iron, thus leading again to the absence of elements essential to life.
Again, a smaller universe would expand so rapidly that matter would not condense by gravity to form stars and planets. But in a bigger universe, stars would be much larger, and this would lead to conditions too unstable for life to be sustained.
In fact, the size and density of the universe is just right for intelligent physical life to develop. This is just one aspect of the ‘anthropic fine-tuning’ argument, popularly known as the ‘Goldilocks effect’.
See Ross, Why the Universe is the Way it is (Baker, 2008), 27-41.