"Because of their sins" means: due to their sins. "They were drowned and admitted into a Fire" means: the Fire became inevitable for them.
Muhammad said: "Because of their sins"—it is said that the meaning is: 'min khatiyatihim' (from their sins), and the 'ma' is supplementary.
﴿مِمَّا خطيئاتهم﴾ أَيْ: بِخَطَايَاهُمْ ﴿أُغْرِقُوا فَأُدْخِلُوا نَارًا﴾ أَيْ: وَجَبَتْ لَهُمُ النَّارُ.
قَالَ محمدٌ: (مِمَّا خطيئاتهم) قِيلَ: إِنَّ الْمَعْنَى: مِنْ خَطِيئَاتِهِمْ، و (مَا) زَائِدَة.
