The more people move away from the guidance of the heavens and the message of the prophets, the more misery and darkness prevails. It is for that reason that Allah sent one messenger after another. {Messengers as bearers of good news as well as of warning in order that mankind should have no plea against Allâh after the (coming of) Messengers. And Allâh is Ever All-Powerful, All-Wise.}(An-Nisâ’:165)

And Allah will never punish a people to whom He sent no messenger. {And We never punish until We have sent a Messenger (to give warning)}(Al-Isrâ’:15).
After Prophet Jesus (pbuh) was sent to mankind and then raised to the heavens above by Allah, humanity suffered from ignorance, injustice and darkness; for monotheistic religions were exposed to misrepresentations and were distorted by falsifiers, who replaced pure monotheism with idolatry and polytheism. They transgressed against Allah Almighty, told lies about Him and insulted the Divine Self. There was no difference between the people of the book and the people of idols concerning their worship and their lives. The light of monotheism, therefore, disappeared under this colossal heap of polytheism and atheism, which made alterations to and forged the word of Almighty Allah. Those who were given the book threw away its covenants and the word of Allah behind their backs, and did not give them even the time of day. They also concealed the truth, spread falsehood and ventured against the prohibitions of Allah. They were heedless of the rights due to Him and the rights of others. In exchange for such concealment they obtained pathetic lofty positions and despicable money, all at a high cost, i.e. the damnation of their souls. This was the case with their superiors who followed their desires and who favored their whims over the truth. Consequently, bloody wars ensued, tyranny appeared and humanity lived in complete, gloomy darkness, which blackened the hearts due to the darkness of disbelief and ignorance, sullied ethics, defiled honor and violated rights. Corruption appeared both in the land and at sea! Any wise man who ponders about the situation would realize that, at this juncture, humanity was dying and would be on the verge of its demise unless Allah made it right by sending a great reformer. This reformer would carry the torch of prophet-hood, and the rays of guidance to illuminate the way for humanity, and guide it to the straight path.
source: islamkingdom