Allah sent numerous Prophets and Messengers (may the peace and blessings of Allah be upon all of them) throughout human history in various locations around the earth. Some of these Prophets are mentioned in the Quran. Among those that are mentioned in the Quran include (not in chronological order) Adam, Abraham, Noah, David, Solomon, Jacob, Job, Jonah, Joseph, Zacharia, John, Moses, Aaron, Salih, Hud, Shoaib, Idrees, Jesus and the final Prophet Muhammad (ﷺ). Each of these Prophets or Messengers were sent to their own people or nation. Prophet Muhammad (ﷺ) was sent for all of mankind (and the Jinn), not just in Arabia but all over the world.
Since Prophet Muhammad (ﷺ) was the last one of these Prophets & Messengers, Allah has commanded his ummah (his followers) to call people to Allah. So the responsibility of calling people to the religion of Islam has shifted from the Prophets & Messengers to the people of the last Prophet (ﷺ). This is evident from the Quran, the Sunnah (recorded in the Hadith) as well as the understanding of the Sahabah (the companions of the Prophet (ﷺ) as they continued to call people to Islam after his life. Therefore, the work of Dawah (calling people to Islam) is an obligation for Muslims, Allah knows best.
The work of calling people to Islam is one of the highest virtues and one of the most rewardable of good deeds. This is because the reward of the good deeds of any and all people that
we call to Islam will be added to our accounts of good deeds. If anyone come to Islam (or Muslims that change their ways back to Islam after having forgotten their way), their who life’s work and anyone they call to Islam and their good deeds are all in our accounts until the Day of Judgment.
And Allah knows best.