Matter and energy may have always existed. Matter and energy may be eternal. The universe must have had a beginning, but not matter and energy, because the beginning of the universe is the big bang, but the big bang is not the beginning of matter and energy, and the big bang only started the current universe, and the big bang did not start the existence of matter and energy. Just as the major theistic religions claim that there is a god that is eternal and that has always been existing (or has existed since ever), there is nothing that makes the belief that matter and energy have always been existing (or have existed since ever) and that matter and energy are eternal and that matter and energy will always exist forever impossible to be right or correct or true. The same defense used by major theistic religions and anyone who believes and follows any major theistic religion to hold their belief that god is eternal and that god has always been existing (or has existed since ever) and that god will always exist forever could also be used to support the possibility of matter and energy being eternal and having always been existing and having been existing since ever and existing forever.

Just as God could have existed without being created, the universe could have existed without having been created. If god doesn’t require a creator to come to existence, then the universe also could come to existence without requiring a creator deity. Why would they believe that God is the only exception from the inability of something to come to existence without a creator?