The idea that the universe began to exist has something to do with Craig's version of the first cause argument. Though Craig rightly says that it need not have begun in a singularity, he also seems quite keen to defend theories which have singularities, so it does look like he thinks there's something significant about them.

If a first cause argument cannot be challenged by any sort of physical discovery or theorising, it seems the pretty empty to me: who are we to tell the universe what it must be like?