There are several possibilities, and hence beliefs, as to when, how, and why (if any such) what we experience as existence came to be. In the past (long ago), our ancestors would hardly have even contemplated such questions (just inventing various easily understood variations), and in the future (if we survive), our descendants will likely have better knowledge than we have currently - but even then, the truth might not be forthcoming. For us now, we are not really in a position to have the true answers, and hence will likely choose one explanation (out of many) for various reasons - usually that which makes sense to us with the knowledge and abilities we have. For me, the honest answer is we don't know but some explanations are less likely than others - especially those relying on old religious textual material. We do seem to have sufficient evidence to justify beliefs as to the age of our current universe but anything beyond that is open to speculation - but then I am not a physicist or astrophysicist.