this is because the disbelievers followed falsehood and the believers followed the truth which is from their lord this is how allah illustrates the examples of people to them.
ذلك بأن الذين كفروا اتبعوا الباطل وأن الذين آمنوا اتبعوا الحق من ربهم كذلك يضرب الله للناس أمثالهم