If we try to understand origin of cosmos from a spiritual angle as detailed in Upanishads (independent spiritual treatises) we would realize that manifestation of Brahman was automatic, not even in its control.
God Almighty, creator of cosmos is called Brahman in Hinduism.
Going back in time when the dissolution of old cosmos (the cosmos previous to the present one) is occurring. At this moment all souls’ atmans in cosmos automatically reached 8.4 millionth manifestation, last in cosmic life cycle.
Spiritually every single living being including human beings reached state of enlightenment and finally moksha salvation.
Devoid of dross impurities within, this is a reality only a seeker, spiritual traveler can understand.
The moment dissolution of old cosmos completes, in absence of dross impurities within the cluster of all pure souls atmans in cosmos carried the volume of half a thumb. This half a thumb, primordial cosmic energy we called Brahman (God Almighty in all its glory) unable to contain itself for long in its prime pure state again explodes with a big bang giving rise to a new cosmos, an entirely new journey of life. And with big bang a new cosmos is formed.
After billions of years into the future when the present cosmos started disintegrating, it will become like a massive black hole, reducing to the size of half a thumb. This is the stage when Brahman, God Almighty regains its original form.
Right from origin of cosmos to dissolution of entire cosmos, everything is minutely detailed in Bhagavad Gita and Upanishads (independent spiritual treatises). A fewer decades before scientists world over debating over big bang issue seemed immature in light of Indian spirituality as everything exists in Hinduism from the very beginning.