PlayStation has a special Loyalty Program called PlayStation Stars, where members collect Points which they can use to redeem special rewards. Those Points can be redeemed in the Rewards Catalog for available items that may include Digital Collectibles, select game titles, and more. One of those rewards are the Super Credit bundles (as well as similar rewards for other games that you play).
Source: N4G PC PS Players Can Get Super Credits for Helldivers 2 Using a PlayStation Loyalty Program