Rational Argument For God
It is irrelevant to ask who created God because we have no knowledge of God being a created entity. Rationally, there must be an uncreated entity in order to deal with the logical problem of infinite regress. The same does not apply to this universe. When we observe this universe, we find tremendous order in it. It is through this order that we derive the laws of nature and are able to do science. Causality that you mentioned above is also a concept that can only be reasonable due to such order. It is also through this order that we derive our aesthetic sense and are able to differentiate between beauty and ugliness. We also find intelligence in this universe. Since in our experience order and intelligence never come into existence without a conscious mind, we are compelled to conclude that this universe is also created. If this universe is created then logically we conclude that it must have a creator. Rational conclusions can be plausible but not necessarily credible unless supported by evidence. Prophets of God provide us with such evidence, consequently granting credibility to our rational conclusion.
Until it can somehow be shown on the basis of evidence that the universe is an effect, this idea shall only remain a conjecture. Also the principle of causation itself will have to be proven beyond any reasonable doubt. There are, however, philosophers e.g. Ghazali and Hume who have raised serious questions on this principle that still remain largely unanswered. When there already exists an evidence based narrative about the universe being a creation of God, any other idea that challenges this narrative cannot be just a speculation. It will have to be credibly established.