"I always understood that it was the universe that was created Ex nihilo, not man.
The Big Bang theory certainly seems to lend credence to that view."
Yes and the Catholic priest who proposed it was accused of injecting religion into science.
Keep in mind that LeMaitre (the priest you speak of) didn't have any physical evidence to back his claims. It wasn't until Edwin Hubble discovered the universe was expanding (a mere two years later) that the idea began to receive vindication. Extraordinary claims require extraordinary evidence, and Hubble found it. If we had accepted LeMaitre's claim without evidence, it would have been a leap of religious faith.
The odd thing about science is that first impressions fade away with evidence. The details of the big bang are still under investigation, but the event was accepted as soon as the evidence appeared.
Same with evolution. It is the hyperliteral interpreters of the Bible who have not accepted the big bang.