@Thomas,
No - he was no atheist and not German either.. He was English, a Franciscan brother and a Scholastic philosopher of some repute. Thomas Aquinas, who lived a century or so earlier would have been very comfortable with him.
However, we have successfully narrowed the question down to the essential issue. Frankly I find the arguments offered in support for the asserted simplicity of the leap to atheism seriously deficient.
A universe that has always existed, but whjch has no creator or designer appears to me to be a contrivance that poses far more questions than it answers. It also leaves us with a problem relative to the Second Law of Thermodynamics.
While singularities, such as the 'big bang', don't, in the mathematical sense, permit such questions as , "what came before it?", or "what caused it?"; that is merely the inevitable result of the insufficiently complex or defective mathematical model that yielded the singularity in the first place. The singularity is a feature of our model for the universe, and not the universe itself - indeed in mathematics "singularity" is a term of art for "undefined". Science is actively attempting to examine the details of the "bang" and to consider larger contexts in which it may be comprehensible - it doesn't accept the finality of the singulatity either.
Questions such as "What is north of the North Pole?" are cute, but no more illuminating than "What is in an empty glass?". Moreover, it does seem odd to encounter one who rejects such meaningless questions and then expresses a willingness to accept the meaningless existence of an eternal universe.