The Great Liberation Tantra

Women were not unfaithful, but devoted to their husbands;
Brahmins, Kshatriyas, Vaishyas, and Shudras lived according to their own conduct. (29)
Worshipping with their own duties, they attained the path of liberation.
When the Satya age passed and the Treta age arrived, seeing the decline of duty, (30)
Mortals were no longer able to achieve their desired ends through rituals prescribed by the Vedas.
Vedic action is the cause of much suffering and requires many resources. (31)
Humans, with minds distracted by worry, are not fit to perform them;
They are unable to perform them or to abandon them, their hearts always agitated. (32)
Therefore, by revealing scriptures that are in the form of Smritis, which contain the meaning of the Vedas, on this earth, for those weak in austerity and private study... (33)

"Not unfaithful," and so on. In that Satya age, there was no disease; they were always healthy. "Endowed with brilliance, form, and virtues," means they were endowed with luster, beauty, and other qualities. (28) (29)

"Worshipping" means they were worshipping the Supreme Lord. "When the Satya age passed" and the Treta age arrived, since mortals (humans) were unable to achieve their desired ends—the fulfillment of their own wishes—through rituals prescribed by the Vedas. Or, "full of many resources" means that which has many requirements. Therefore, it is "the cause of much suffering," meaning it is the producer of many hardships. Or, that which is performed or accomplished with many hardships is "cause of much suffering." Therefore, humans, with minds distracted by worry, were not fit to perform such Vedic rituals. Or, because they were "always agitated in heart" and heard of various defects in performing Vedic rituals, they were unable to perform them and unable to abandon them because of their difficulty. At that time, seeing the "decline of duty"—the transgression of duty or the reversal of duty—scriptures in the form of Smritis, which contain the meaning of the Vedas, were placed on the earth.