Prophets have come through the ages to remind people of the blessings of God, ask them to fulfill their promises to God, invite people to the right path, and promote the teachings of earlier prophets. Verse 44 of Surah Al-Mu’minun reads “Then We sent Our Messengers in succession. Yet whenever its Messenger came to a nation they belied him, so We made them follow others, and We made them but as tales, so begone the nation who did not believe!”
Seeing prophets’ call against their interests, infidels resisted the invitations and tried to forget the teachings. So there was a need for reminding humans of God and hence, divine prophets were sent by God one after the other.
Talking about the mission of prophets, Imam Ali (AS) also points to this issue: “God sent His messengers to them to ask people fulfill their inherent pact, remind them of His forgotten blessings, offer final arguments with propagation, and reveal the hidden treasures of intellects in the light of their teachings” (Nahj al-Balagha, Sermon 1)
This divine tradition of course had enemies that caused the prophets to face difficulties in the way of guiding the people.
“In order to implement the tradition of divine testing, God sent his prophets to the people one after the other, so that if one left, another would take his place, but every prophet was denied according to people’s long-standing tradition,” writes Ayatollah Naser Makarem Shirazi in Tafsir Nemooneh.