It is said the Samkhya school outrightly rejects the existence of God and considered by many, an atheistic school. However, the sixteenth century Vaishnavite scholar Vijnanabhiksu accepted Samkhya to be valid and he tried to find the unity between the 3 Astika schools or Darshanas- Vedanta, Yoga and Samkhya. Now how is this possible? Vedanta and Yoga Darshanas strongly accept the existence of God but Samkhya outrightly rejects it. Moreover, Vijnanabhiksu was a Vaishnava and Vaishnavas usually are vocally opposed to the Samkhya school.
Vijnanabhikshu believed that Kapila, the founder of the Samkhya school, was an incarnation of Vishnu, and that Kapila just pretended to reject the existence of Ishwara in order to deceive people. But this isn't like the case of Vishnu's incarnation Buddha, who deceived the Asuras in order to hurt them. Rather, Vijnanabhikshu argues that Kapila deceived people for their own benefit. The idea is that if people believe in Ishwara, they will seek to have the Aishwarya or lordliness, i.e. the same powers that Ishwara has, and the pursuit of such powers will distract them from attaining Jnana. Whereas if people think there's no such thing as Ishwara, they won't be attracted to such powers. Here is what Vijnana Bhikshu says near the beginning of his commentary on the Samkhya Sutras:
[I]t is in this [i.e. Samkhya] Shastra that the exclusion of Ishvara has been made for practical purposes only, and it is, therefore, proper to translate it as designed to produce indifference towards the lordliness of Ishvara. The idea of Samkhya teachers is that should eternal lordliness be not contravened in the manner of the Lokayatika or sensualist doctrines [i.e. Charvaka], then Chitta or the inner sense being drawn away towards it by the vision of perfect, pure and eternal lordliness, there would arise an obstacle to the formation of the habit of Viveka or discrimination between the Self and the Not-Self.
So to sum up, in Vijnanabhikshu's view, the atheism of the Samkhya school is false but is useful for obtaining Jnana! Specifically, obtaining knowledge of Purushas, Prakriti, and the 23 evolutes of Prakriti, which Vijnanabhikshu saw as essential for attaining Moksha.