SB 6.18.29

evaṁ striyā jaḍībhūto
 vidvān api manojñayā
bāḍham ity āha vivaśo
 na tac citraṁ hi yoṣiti
evam — thus; striyā — by the woman; jaḍībhūtaḥ — enchanted; vidvān — very learned; api — although; manojñayā — very expert; bāḍham — yes; iti — thus; āha — said; vivaśaḥ — under her control; na — not; tat — that; citram — astonishing; hi — indeed; yoṣiti — in the matter of women.
Although Kaśyapa Muni was a learned scholar, he was captivated by Diti’s artificial behavior, which brought him under her control. Therefore he assured his wife that he would fulfill her desires. Such a promise by a husband is not at all astonishing.