وَقَدْ جَاءَهُمْ رَسُولٌ مُبِينٌ ثُمَّ تَوَلَّوْا عَنْهُ
Yet a manifest messenger had come to them, and then they turned away from him.
This account of prior rejection provides the contextual evidence for interpreting annā lahumu al-dhikrā as improbability. A messenger had already come with clear guidance, yet the audience turned away.
The rhetorical interpretation is therefore grounded in the sequence of verses, not in a dictionary replacement of annā by a single English expression.