The author was not trying to disprove the existence of 'God' but rather was arguing that those theories that conclude that 'God' caused the existence of the Universe, are flawed.

In fact, as I've pointed out elsewhere, the author assume that a 'God' exists, at least for the sake of the argument regarding the cause of the Universe, as is clear from the article's title.

There is no point in attempting to disprove the existence of 'God' for there is precisely zero evidence that such an entity is other than the creation of human beings.

Until someone can give any reasonable argument for the existence of such a bizaree entity as an omnipoten entity such as 'God', particularly given that human beings actually believed that they were that 'God' or, more accurately, group of gods, before the various religions were formalised, there is no reason why anyone should waste time, effort, and intellectual energy in attempting to disprove that existence.