There are really two problems: "Why something and not nothing?" and "Why this and not something else?" / the first you can maybe just ignore because, demonstrably, something exists / the other question is rough, our universe is weirdly specific. there's only one universe so why this specific one / multiverses offer an answer to first origins that are compatible with a scientific worldview / the reason why things are this way and not some other way is that somewhere else, things are different
Scientists call this the "fine-tuning problem" / the Standard Model of physics has about 25 arbitrary numeric constants that are just hardcoded into the equations / but these numbers are not quite arbitrary *enough*, that is some of them if adjusted even slightly appear to produce a universe with no useful chemistry and as far as seems possible no life / they seem "finely tuned" / if the constants are random, how did we luck out to get the ones supporting self-aware structures such as ourselves?