This is the style of Quran to explain a thing, if required, at some later stage. Such verse are called explanatory verses. These are usually answers to the questions, for example, see 2: 219 and 4:174 or without it, but it is about a thing or problem which could have been understood with deliberation, but God out of His favour explained it to save the Muslim from differences in opinions. God does it to let His audience first make an effort to understand His injunction, and in this process they raise questions and then they are provided with answer. This technique is used in teaching.

Later explanation was a responsibility God has taken upon Himself and mentioned it here:

إِنَّ عَلَيْنَا جَمْعَهُ وَقُرْآنَهُ ‎﴿١٧﴾‏ فَإِذَا قَرَأْنَاهُ فَاتَّبِعْ قُرْآنَهُ ‎﴿١٨﴾‏ ثُمَّ إِنَّ عَلَيْنَا بَيَانَهُ

“upon Us is its collection and recital. So, when [at that time] We recite it, follow that recital of it. Then upon Us is to explain it [for you wherever need be].” (75: 17-19)