Stephen Hawkings is a physicist and he needs to put any idea of God outside of the domain of physics. (a)
Georges LeMaitre was (WP Hubble-Law) a belgian priest and the BBT leaves intact the divine intervention as a justification to the act of the creation of the universe/matter, and it appraises to the Catholic Church and other religious positions.
If you beleive in ONE single BB then you are a priviledged observer of something that begs the question: And before? and why?
(gravity in the sentence is not about gravity but only: there is a law...)
the universe can and will create itself from nothing.
Is a circular reasoning as you say, even worst: create itself (like god!); from nothing? (a free lunch!). From 'nothing' we can not get 'something'.
I think that Spinosa's view is more adequate to a physicist:
The Universe was, is and will be ALL with no start nor end. The event of matter creation, we use to call it BB, is a repeatable event.
This way I do not need to call for any entity exterior to the universe.
(a) - if God exists, or not, is a different question, and is outside of the domain of this site.
In Physics we can not invoke any transcendental entity to be 'a cause'.