If (from a religious perspective) god supposedly created all the religious rules,
Not all religions subscribe to this. Buddhism for example doesn't really talk about who created the rules, and instead arrives at the rules empirically (See the 4 noble truths).
then why does every religion follow different rules?
Different religions have different answers to this. Christianity, for example, views its own rules as an update of the previous rules laid out in Jewish scripture.
Orthodox Sunni Islam, on the other hand, maintains that the rules of all the great monotheisms were the same, since they share the same divine origin, but that human authors corrupted past scriptures (i.e. the Torah and the New Testament) and that Islamic scripture is, among other things, a correction of those errors that restored the original rules for humanity.
In both cases, the tradition acknowledges different sets of rules, but considers only one set of rules to be correct, and provides an explanation for why that is the case.
Is this a strong argument against the idea that religious rules are divine in origin?
No it isn't. Some religious and philosophical traditions don't see any problem in the diversity of religious rules and rituals. In Hinduism, the Bhagavad Gita states (I forgot the exact verse - I will need to look for it): God (Or The Truth - depending on the translation) is one, but the paths to Him are many.
Similarly some schools of Sufi Islam consider that there are many paths to God, Islam is just one of them. See Attar's "The Conference of The Birds" or several of Rumi's poems - again I need time to dig up the relevant verses.
More recently, Aldous Huxley (who was himself an atheist) develops this idea by presenting examples from the various religious traditions of the world in his book "The Perennial Philosophy". He argues that all (or most religious traditions) are just variations on a set of basic truths that is called the perennial philosophy.