This particular devastation actually took place not during the night of Lord Brahmā but during his day, for it was during the time of Cākṣuṣa Manu. Brahmā’s night takes place when Brahmā goes to sleep, but in the daytime there are fourteen Manus, one of whom is Cākṣuṣa Manu. Therefore, Śrīla Viśvanātha Cakravartī Ṭhākura comments that although it was daytime for Lord Brahmā, Brahmā felt sleepy for a short time by the supreme will of the Lord. This short period is regarded as Lord Brahmā’s night. This has been elaborately discussed by Śrīla Rūpa Gosvāmī in his Laghu-bhāgavatāmṛta. The following is a summary of his analysis. Because Agastya Muni cursed Svāyambhuva Manu, during the time of Svāyambhuva Manu a devastation took place. This devastation is mentioned in the Matsya Purāṇa. During the time of Cākṣuṣa Manu, by the supreme will of the Lord, there was suddenly another pralaya, or devastation. This is mentioned by Mārkaṇḍeya Ṛṣi in the Viṣṇu-dharmottara. At the end of Manu’s time there is not necessarily a devastation, but at the end of the Cākṣuṣa-manvantara, the Supreme Personality of Godhead, by His illusory energy, wanted to show Satyavrata the effects of devastation. Śrīla Śrīdhara Svāmī also agrees with this opinion. The Laghu-bhāgavatāmṛta says:

madhye manvantarasyaiva
 muneḥ śāpān manuṁ prati
pralayo ’sau babhūveti
 purāṇe kvacid īryate

ayam ākasmiko jātaś
 cākṣuṣasyāntare manoḥ
pralayaḥ padmanābhasya
 līlayeti ca kutracit

sarva-manvantarasyānte
 pralayo niścitaṁ bhavet
viṣṇu-dharmottare tv etat
 mārkaṇḍeyeṇa bhāṣitam

manor ante layo nāsti
 manave ’darśi māyayā
viṣṇuneti bruvāṇais tu
 svāmibhir naiṣa manyate