Also, by ascribing the verb to their commerce - although rightly it should have been ascribed to themselves; that is 'but they gained no profit in their trade' (fa-mâ rabihû fi tijâratihim) - is a sign that in no respect, in none of its particulars or conditions or means, does their commerce yield any benefit, unlike in some businesses where no profit is made on the products but some benefits may accrue in other particulars or their services. The dissemblers' trade is pure evil and undiluted harm. Ascribing the verb to the trade here resembles the saying: "Nâma layluhu (his night slept)" instead of "nâma fi'l-layl (he slept in the night)." The former means that besides himself sleeping, the night was hushed and silent as though sleeping, and nothing disturbed him.
"And they are not rightly-guided (wa mâ kânû muhtadîn):" that is, just as they have lost their capital, so have have they lost their way. This is linked and associated with the parabolic "ishtaraw (have purchased)," as was the preceding phrase. It also hints obliquely at "guidance for those who fear Allâh (hudan li'l-muttaqîm)" at the start of the sura. As though it is saying: "The Qur'an offered them guidance, but they did not accept it."