I can easily see the theological implications of the issue, but in principle it's not all that different from the issue of the origin of life on earth. If a natural cause of life can be demonstrated, we all know that there are theological concerns. Ditto for the Big Bang itself. But I still suggest that those who seek to understand such phenomena aren't necessarily motivated by an anti-theological purpose. There's always the time-honored motive of plain old curiosity. Some people are simply attracted to unsolved problems.
If there is the possibility of a comprehensible, natural cause for the Big Bang, wouldn't you really like to know what it is? Notwithstanding the theological implications? I suspect that you would. And that perfectly human curiosity doesn't mean you have atheistic tendencies.
Of a truth, all that either of us can actually know of a person's motives is their own testimony - which may be true or not.
What I have deduced of Hawking's motives has to do with the content of his lecture and indeed, I may be wrong because I cannot truly know his thoughts. What raised my suspicion was his mention of Young Earth Creationism without an apparant purpose in the context of the lecture except to ridicule. The phrasing of the subsequent sentences and paragraphs only added to that impression in my view.
By contrast, Burt Ovrut - who also explores the possibility of a Big Bang-less beginning in his ekpyrotic cosmology - does not go off-subject at all. Thus I have had no reason to raise an eyebrow when reading or listening to his thoughts.