«وَجَعَلْنَا اللَّيْلَ لِبَاسًا»
We made the night a covering.
Al-layla can be analyzed as the first object of jaʿalnā and libāsan as the second. Clothing evokes covering and enclosure, making the enveloping quality of night tangible.
The expression does not claim that night is literally an article of dress. The imagistic predication explains why the chosen noun conveys more than a bare statement that night is dark.