It is widely believed that this vast infinite universe stems from one Reality - the one Consciousness. Then, why are there so many different life forms that experience pain and pleasure? And, why are so many life forms that are at the lower levels of consciousness (plants and trees) ? Why did that One Reality manifest in so many different forms? Why did not that One Ultimate Pure Reality remain dormant?
There are many theories on creation that exist in all religions. Most of these theories are exist only to temporarily satisfy the human intellect in its current state of ignorance (duality) Ultimately, (Advaita) Vedanta refutes all creation theories such as the big bang. One of the most famous of these commentaries is by Gaudapada, Adi Shankaracharya’s teacher, who has written the Karika on the Mandukya Upanishad.
Indeed, the one consciousness is the substratum upon which the universe rests. However, consciousness being complete, all powerful, all pervading, is desireless, and being without desire there is no need to create anything. In a sense, it is dormant as you say. How does one explain this dynamic universe then? From the Advaita standpoint, the cause of the universe is individual ignorance, which veils the ultimate reality and projects a dualistic world instead. What is true is not seen, and what is untrue is projected - such is the nature of ignorance.
Individual consciousness started out of ignorance of Self. Like pure consciousness, ignorance is uncaused (we cannot point to a time it did not exist). Ignorance then creates desire, and desires creates action. Action then bears its fruit and further increases desire. The wheel of samsara thus continues propelled by the Ajnana (Ignorance) -> Kama (Desire) -> Kriya (Action) -> Karma Phala (Fruits of action) Each life form gives the conditioned consciousness (the Jiva) the ability to enjoy and suffer the fruits of its karma in a unique manner. A single environment/form cannot satisfy all desires. Thus, different life forms (and different worlds) exist because the desires are so varied in different types of creatures.
The above is a radical shift in the way we perceive the world. We are all used to thinking of ourselves as small objects in a vast universe. As opposed to that, the idea here is that the entire universe exists because you created it - albeit out of ignorance, much like you create an entire dream world in your sleep with nothing but the mind.
With Love,
Sudhir