﴿ وَلَوْ شَآءَ ٱللَّهُ لَجَعَلَهُمْ أُمَّةًۭ وَٰحِدَةًۭ وَلَٰكِن يُدْخِلُ مَن يَشَآءُ فِى رَحْمَتِهِۦ ۚ وَٱلظَّٰلِمُونَ مَا لَهُم مِّن وَلِىٍّۢ وَلَا نَصِيرٍ ﴾

“Now had God so willed, He could surely have made them all one single community: none the less, He admits unto His grace him that wills [to be admitted] whereas the evildoers shall have none to protect them and none to succour them [on Judgment Day].”

And had God willed He would have made them one community in other words following one religion and that is Islam; but He admits whomever He will into His mercy and the evildoers the disbelievers have neither guardian nor helper to ward off the chastisement from them.