Ironically, they broke up into sects only after the knowledge had come to them, due to jealousy and resentment among themselves. If it were not for a predetermined decision from your Lord to respite them for a definite interim, they would have been judged immediately. Indeed, the later generations who inherited the scripture are full of doubts.
وَما تَفَرَّقوا إِلّا مِن بَعدِ ما جاءَهُمُ العِلمُ بَغيًا بَينَهُم وَلَولا كَلِمَةٌ سَبَقَت مِن رَبِّكَ إِلىٰ أَجَلٍ مُسَمًّى لَقُضِىَ بَينَهُم وَإِنَّ الَّذينَ أورِثُوا الكِتٰبَ مِن بَعدِهِم لَفى شَكٍّ مِنهُ مُريبٍ
wa maa tafarraqooo illaa mim ba’di maa jaaa’ahumul ‘ilmu baghyam bainahum; wa law laa Kalimatun sabaqat mir Rabbika ilaaa ajalim musammal laqudiya bainahum; wa innal lazeena oorisul Kitaaba mim ba’dihim lafee shakkim minhu mureeb