Why did people start believing in Islam religion?

Answer 1

There are many reasons as to why people may become Muslim. From a non-religious perspective I could say:

• Because they were indoctrinated. Their parents believed it, the belief was imposed on their impressionable mind, and they had no choice.
• They interpreted a natural (though unusual/improbable) phenomenon as a miracle.
• Their mind played tricks on them and they saw/heard something demonstrating the existence of Allah.
• They concluded that Allah exists because there is no alternative explanation available to them which seems as reasonable.

In the past tense, you may be referring to the time when Islam was starting. People became the first Muslims because Muhammed was a very respected member of their community. Although as I understand it, the first Muslims were ostracised, their numbers continued to grow in their independent community. The alleged circumstances of the foundation of Islam give great credence to the truth of the faith. The isolation of Muhammed at the time when the revelation came to him strongly implies that the Qur'an could only have come from God. With such overwhelming evidence, conversion was easy.

From the opposite perspective I could say:

• Because Allah revealed himself to them
• Because Allah's intervention into the world was seen by them, so they believed
• Because they heard Allah speak to them, or they saw the Prophet Muhammed walking towards them across the desert sands

There are other reasons, of course. I could not speak entirely on behalf of both sides, so there will be things to be added.

Answer 2

Islam is an Arabic word that means "submission". So, Islam in its universal sense is full submission to God, the one and only one God. In this understanding, God message to Prophet Mohamed is not isolated or different from God message to all His prophets from including Noah, Abraham, Ismael, Isac, Jacob, Joseph, Moses, David, Solomon, ..., Jesus, until his last prophet Mohamed (peace upon them all) but it is a continuation to previous God messages and previous prophet missions. The basic principle of all God messages is to call people to worship God, the one and only one God and to call mankind to full submission to God, the one and only one God.

Judaism is the religion per God revelation of Torah to prophet Moses. Christianity is the religion per God revelation of the Injeel (Gospel) to prophet Jesus. The very name Islam is the religion per God revelation of Quran to prophet Mohamed.

Islam religion as the last God mission to mankind is based on simple teachings and straight forward rules that logic and understandable to all mankind anywhere anytime. The teachings are covering all aspects of one's life and offer practical balance between one's human desires and God requirements from him (see related questions on Islam major teachings, Islam morals, and Islam 5 pillars).

Quran as God holy book, for being the last heaven holy book, is protected (by God will) from any alterations or falsification or deviations until the day of Judgment. In the meantime, as Quran is the last holy book, Quran includes built-in historical and scientific evidences that prove the Quran authenticity and that Quran is the real words of God (see the related question below: why Quran was revealed? for more information).

Prophet Mohamed as a prophet, for being the last God prophet to mankind, is the real model for any one who wants to follow the right path to God during all his life practices. You find this in prophet Mohamed the preacher, the husband, the father, the friend, the statesman, the warrior, the negotiator, the adviser, the judge, the merchant, the shepherd, ..., in all aspects of life.

Muslims, as followers of Islam, for being followers of the last religion, are commanded to believe in all God prophets and in all God holy books. They are required to call for God path with wisdom and peaceful advice (see the related question below: what are Quran Golden Rules? for more information).

Note:

• Name Mohamed may spelled Mohammed, Mohammad, Muhammad, or Muhammed.

• Quran may be spelled Qura'n, Quraan, Kuran, Kura'n, Kuraan, Koran, Kora'n, or Koraan.