(He was so) because he had wealth and children. When Our Ayat are recited to him, he says;"Tales of the men of old!"
Allah is saying, `this is how he responds to the favors that Allah has bestowed upon him of wealth and children, by disbelieving in Allah's Ayat and turning away from them while claiming that they are a lie that has been taken from the tales of the ancients.'
This is similar to Allah's statement,
ذَرْنِى وَمَنْ خَلَقْتُ وَحِيداً وَجَعَلْتُ لَهُ مَالاً مَّمْدُوداً وَبَنِينَ شُهُوداً وَمَهَّدتُّ لَهُ تَمْهِيداً ثُمَّ يَطْمَعُ أَنْ أَزِيدَ
كَلَّ إِنَّهُ كان لاٌّيَـتِنَا عَنِيداً سَأُرْهِقُهُ صَعُوداً
إِنَّهُ فَكَّرَ وَقَدَّرَ فَقُتِلَ كَيْفَ قَدَّرَ ثُمَّ قُتِلَ كَيْفَ قَدَّرَ
ثُمَّ نَظَرَ ثُمَّ عَبَسَ وَبَسَرَ ثُمَّ أَدْبَرَ وَاسْتَكْبَرَ
فَقَالَ إِنْ هَـذَا إِلاَّ سِحْرٌ يُوْثَرُ إِنْ هَـذَا إِلاَّ قَوْلُ الْبَشَرِ
سَأُصْلِيهِ سَقَرَ وَمَأ أَدْرَاكَ مَا سَقَرُ
لَا تُبْقِى وَلَا تَذَرُ لَوَّاحَةٌ لِّلْبَشَرِ عَلَيْهَا تِسْعَةَ عَشَرَ
Leave Me alone (to deal) with whom I created lonely (without any wealth and children etc.). And then granted him resources in abundance. And children to be by his side. And made life smooth and comfortable for him. After all that he desires that I should give more.
Nay! Verily, he has been opposing Our Ayat. I shall oblige him to face a severe torment!
Verily, he thought and plotted. So let him be cursed, how he plotted! And once more let him be cursed, how he plotted!
Then he thought. Then he frowned and he looked in a bad tempered way. Then he turned back, and was proud.
Then he said;"This is nothing but magic from that of old, this is nothing but the word of a human being!"
I will cast him into Hellfire. And what will make you know what Hellfire is
It spares not (any sinner), nor does it leave (anything unburned)! Burning and blackening the skins! Over it are nineteen (angels as keepers of Hell).
(74;11-30)
Then Allah said here,
سَنَسِمُهُ عَلَى الْخُرْطُومِ