What primarily drove the collapse of the earliest gas clouds lacking heavy elements?

Direct gravitational instability driven by sheer mass.

In modern stellar nurseries, the presence of heavier elements allows gas clouds to radiate heat away efficiently. This cooling enables the cloud to fragment into numerous smaller pieces, leading to the formation of many lower-mass stars. However, the metal-free gas clouds of the early universe lacked this efficient radiative cooling pathway. Consequently, the only viable mechanism for the cloud to overcome the immense temperature barrier and collapse was through direct gravitational instability, where the sheer magnitude of the cloud's mass overwhelmed internal pressure until deep into the collapse process, leading to a rapid, free-fall scenario.