Tafsir of Al-Anbiya' 21:77

(And We saved him from the people who denied Our signs) meaning: We protected and shielded him from them by destroying them and delivering him. It is also said: We gave him victory over them; thus, min (from) carries the meaning of ‘ala (over/against). Some have said that the verb "to grant victory" (nasara) is used with both ‘ala and min. According to al-Asas, one says: "God Almighty granted him victory ‘ala (against) his enemy," and "He granted him victory min (from) his enemy." A distinction is drawn between the two: using ‘ala indicates mere assistance, whereas using min implies that such assistance entails taking vengeance upon the enemy and prevailing over them.

(Indeed, they were a people of evil) deeply immersed in wickedness. This sentence serves as the justification for what preceded it and as a preamble to what follows in His saying, Exalted is He: (So We drowned them, all of them.)

Indeed, denying the truth and immersing oneself in evil are actions that inevitably result in destruction, as seen in the nations of old. Regarding the accusative case of ajma'in (all of them), it is said that it is a hal (state/adverbial) referring to the attached pronoun in the verb aghraqnahum (We drowned them)—though this view is questionable, as you can see. Abu Hayyan stated that it is an emphatic particle (ta’kid) for that pronoun. The use of ajma'in as an emphasis not preceded by kull (all) occurs frequently in the Quran; this serves as a refutation of Ibn Malik’s claim that such usage is rare, whereas its use following kull is common.