This is the dichotomy for an atheist regarding how and why there is a material universe, theists have at least one extra option, God created the universe.
The reason its a problem is because "stupid physicists" seem to think they have proven the universe is not eternal, it doesn't just violate entropy but also logic, as an eternal material past means you can never traverse back to any point in time that can be considered "now", even time came into existence ex nihilo.
However a universe from nothing is also impossible, logically, philosophically and mathematically (0+0=0) so the two explanations for an atheist for the existence of the universe are falsified easily using logic, reason, math and rationale, thus making atheism impossible, leaving a universe created from an immaterial phenomenon that is omnipotent in order to create, omniscient in order to know how and what to create, omnipresent due to it being infinite in its ontology and omnibenevolent as in its maximal attributes.