Op, let me give you an example of atheist scientists. Scientists first came up with the static universe theory. Then we found the universe continue to expand and we came up with the Big Bang theory. The problem, however, are several fold. We have a magnetic Monopole problem.
The universe should not be flat given the Big Bang. It is flat, not curved. We should be able to see the Big Bang or at least its beginnings, but the further we look back, nothing. The galaxy is not uniform, big problem for Big Bang. We must have dark matter and dark energy for the universe to exist. We can't find any. There are many more.
The biggest problem is that the universe is so delicately balanced, that a single explosion could not possibly have created this kind of balance. The mathematical odds make it all but impossible. Thus atheist scientists had to come up with another theory to combat this. Thus the multi-universes theory that holds that universes are being created all the time (like water boiling in a pot creating bubbles and the bubbles represent universes). No proof whatsoever, but they are going with it. Why? Because they can''t bring themselves to acknowledge a designer. So they make up theories to account for things the Big Bang does not account for.