Science will never explain why there are laws of nature covering the behaviour of all physical phenomena. This is because scientific explanation of the operation of some lower-level law says that it holds because of the operation of some higher-level law under certain physical conditions.
Thus, science explains the operation of Galileo’s law of fall on earth by the operation of Newton’s laws of gravity on earth in virtue of earth having a certain mass. Today it is trying to explain the operation of the four forces (gravity, electromagnetism, the weak and strong forces) by a “theory of everything” in virtue of some feature of the present circumstances of our universe. Any “theory of everything” will consist of some very highest-level law (or laws). All that the universal operation of such a law amounts to is the enormous coincidence that every physical object has precisely the same powers and liabilities to act as every other physical object – for example, to attract and repel every other physical object in accord with some general formula. This coincidence would, because of the very nature of scientific explanation, be always scientifically inexplicable.
Science will also never explain why that highest-level law (or laws) eventually produced a universe in which there is a planet on which human beings have evolved. It may well be that our universe belongs to a multiverse, in which there are many universes governed by different lower-level laws. But our only grounds for supposing that there is such a multiverse are that the postulation of such a multiverse governed by a highest-level law and having some general physical features (such as an eternally expanding vacuum space) explains the coming into being of our universe. Yet in order for this to happen, the multiverse must have a certain sort of general law and general features. For there are innumerable logically possible multiverses governed by different laws with different general features which would never produce a universe in which there is a planet where human beings could evolve. So if there is a multiverse, what science will never explain is why the multiverse is of such a kind as to produce a universe “fine-tuned” to produce humans.