In ancient time, God had sent the Saviors/Prophets to various parts of the world to teach mankind. Each of them had appeared at different times. They had use different methods of teaching to suit the prevailing cultural background.
The origins of Hinduism can be traced to the India sometime between 4000 and 2500 BCE. Hinduism is commonly thought to be the oldest religion in the history of human civilization. The purpose of life is to understand this truth and to understand one’s eternal identity as soul. Thus, it is important to use the opportunity of a current human being to accumulated good deed to unite with God.
Taoism was founded, 550 BC, by Lao-Tse, a contemporary of Confucius in China. Taoism began as a combination of psychology and philosophy which Lao-Tse hoped would help end the constant feudal warfare and other conflicts of his time. His writings, the Tao-Te-Ching, describe the nature of life, the way to peace and how a ruler should lead his life.
Shkyamuni Buddha, 560 BC, had come to this world much earlier than Christ. His teachings and practice come under the heading of Dharma, which means Truth and the path to Truth. His teaching on the Truth (Dharma) had only spread eastwards to Asia. Hence, the people in the Middle East did not get to hear the Dharma or God’s word.
Palestine was in a poor moral state. As such, God decreed Jesus to spread the Truth to the people there. Only the Truth can bring true salvation. “I am the way and the truth and the life' (John 14:6)
When both the Buddha and Jesus teaching failed to reach Saudi Arabia, this time God sent Prophet Muhammad there 610 AD. Prophet Muhammad spoke the Islam as the only way back to Allah. Islam teaches that Allah created humans to be guardians of His creation. In other words, nature does not belong to us to do with as we wish, but is entrusted by Allah to our safe-keeping.
By then, many people in each continent realized and learned that there is the Almighty God, and we understand that when one committed mortal sin, he would eventually go to hell. We all anticipate that when the time comes, all of us can be in heaven with God.
Different religion advocate the idea of one God. Wouldn't that be more than one God, and how do we reconcile this? How many Gods do we have? Is the God of the Spain the same as that of the Americans? Of the Japanese? Of the Chinese? But of course! There is only one God. It varies in languages only. Like the Bible, we all have it, but in different translation. Even English translation comes in many versions. The differences are significant greater in various languages. Your Bible might be in English or in Filipino version, mine might be in Chinese version; Christian calls God as My Lord or Heavenly Father, Hinduism speaks of Krishna, Filipinos talks of Panginoon, the Islam calls as Allah. But they agree on one thing: there is only one God. However, if you were to add the number of Gods quoted by them, it is certainly more than one! Because of the geographic and cultural difference, God has different names. All these religions are actually referring the same God.
As the judgment Day gets closer, God wants to save more people to bring them back to Kingdom of Heaven, the heavenly mandate additional saint to save us.
History Timeline of World Religions and its Founders