2/89 — Though they recognised it
"Formerly they used to pray for victory by it against those who covered over; but when what they recognised came to them, they rejected it."
يَسْتَفْتِحُونَ — root f-t-ḥ: to open. This pattern means "to seek an opening", that is, to ask for victory and the upper hand. According to what is transmitted, they claimed that they would prevail with the coming of the awaited prophet.
فَلَمَّا جَآءَهُم مَّا عَرَفُوا۟ كَفَرُوا۟ بِهِۦ "when what they recognised came to them, they rejected it"
The choice of word is exact: "what they recognised". There is knowing, there is recognising, there is no acceptance. The definition of unbelief in the sixth verse of the sūra — covering over what is known — is seen here at its plainest. The Qurʾān sharpens this further a few verses later: "They recognise it as they recognise their own sons" (al-Baqara 2/146).
The fulfilment of the expectation did not satisfy the expectation. Because what was expected was not really a prophet but preferment; when the prophet came and the preferment passed to another, the expectation lost its meaning.