There are many reasons as to why people may become Muslim. From a non-religious perspective I could say:
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:
There are other reasons, of course. I could not speak entirely on behalf of both sides, so there will be things to be added.
Stop believing in your present religion. Start believing in a different religion.
Islam
It depends on how strictly the people and their leaders practice their religion. People have different interpretations of Islam the reason why is that Muslim countries don't want the youth to start going away from the religion of Islam . Islam is a very strict religion but for a reason
Islam religion was originated by start of universe creation. Refer to related questions below.
Islam started by start of universe creation. Refer to related question below.
Islam started by start of universe creation. Refer to question below for details.
The empire of Arabia.
There is only one kind of Islam religion and it did start in Saudi Arabia and Arabs were the first Muslims
Yes. Islam is an importunity religion. It is God religion since start of universe creation and even befog, Refer to questions below for details.
circa 600AD.
Islam started by start of universe creation and even before. Refer to question below for details.
the importance is that that is were the religion got its start without the start there would be no religion and so you can see there is a very big importance in the beginning of the religion.