that is because those who disbelieved followed falsehood whereas those who believed followed the truth that came to them from their lord. thus does allah set forth to people parables showing their true state.
ذلك بأن الذين كفروا اتبعوا الباطل وأن الذين آمنوا اتبعوا الحق من ربهم كذلك يضرب الله للناس أمثالهم