And mankind were but a single community, then they disagreed. And had a word not gone forth from your Fosterer, the matter in which they had disagreed among themselves would have been settled (once for all).
Human beings are great grand children of Adam and Hawwa (PBT) with a single religion ‘Al Islam’. but people differed to such an extent that there are not only many religions but also sects in every religion. The time of the day of judgement is fixed otherwise Allah (SWT) would have settled once for all who is right and who is wrong i.e. this will be decided on the day of judgment.