You are reading a tafsir for the group of verses 28:78 to 28:79

إِنَّمَا أُوتِيتُهُ عَلَىٰ عِلْمٍ عِندِي (This is given to me because of knowledge (I have) with me- 28:78). Some commentators are of the view that "knowledge" in this sentence refers to the understanding of Torah. As reported in some narrations, Qarun remembered Torah by heart and was an authority on it. He was one of the seventy scholars whom Sayyidna Musa (علیہ السلام) had selected for Miqat (the appointed time and place for having conversation with Allah). But he became conceited on his knowledge, and regarded it as his personal achievement. The object of his above-referred utterance was to convey that whatever wealth he had possessed was the direct result of his personal skill and intelligence. Hence, he himself had the right on it, and that no one had done any favour to him.

However, it is more plausible in the context that the knowledge he was referring to as the basic cause of his being wealthy, was the understanding and skill of managing trade and industry, which brings in wealth. Thus the meaning is that whatever wealth he had collected had come to him as a result of his personal skill and efforts, and there was no favour of Allah Ta’ ala involved in it. What the foolish conceited man had ignored was that his skill, understanding, and experience were also the gift of Allah. He could not have gained them on his own.

أَوَلَمْ يَعْلَمْ أَنَّ اللَّـهَ قَدْ أَهْلَكَ مِن قَبْلِهِ (Did he not know that Allah had destroyed, from the generations before him...28:78). The real answer to Qarun's assertion that he had collected all his wealth by his personal skill and efforts is the one mentioned above; that even if it is accepted for a moment that he had acquired his wealth by his personal skill and knowledge, the point is that this knowledge and experience was also the gift of Allah Ta’ ala. But in order to bring home the more important aspect of the subject, the Qur'an has stated that the abundance of wealth is of no avail and is devoid of merit, nor does it help in distress. As a proof of that, the example of the wealthy from the earlier generations has been quoted, that when they disobeyed and rejected the truth, they were suddenly caught by the torment of Allah Ta’ ala.