Rushdie writes in his memoir Joseph Anton that he studied the early history of Islam at university. (He’s writing about himself in the third person, so “he” here is Rushdie.)
 was the year he found out about the satanic verses. In Part Two of the History Tripos he was expected to choose three ‘special subjects’ from a wide selection on offer, and concentrate on those. He chose to work on […] a third subject, offered, that year, for the first time, titled ‘Muhammad, the Rise of Islam and the Early Caliphate’. […] So came about a strange state of affairs. The special subject […] had not been offered before; and in that academic year, 1967-8, only this one, obdurate student took it; and the following year, owing to lack of interest, it was not offered again. For that single student, the course was his father’s vision made real. It studied the life of the Prophet and the birth of the religion as events inside history, analytically, judiciously, properly. It might have been designed especially for him. […]
The historical record was incomplete, but most of the major collections of Hadith, or traditions, about the life of the Prophet—those compiled by Ibn Ishaq, Waqidi, Ibn Sa’d, Bukhari and Tabari—told the story of an incident that afterwards became known as the incident of the satanic verses. The Prophet came down from the mountain one day and recited the sura (number 53) called an-Najm, the Star. It contained these words: ‘Have you heard of al-Lat and al-Uzza, and al-Manat, the third, the other one? They are the exalted birds, and their intercession is greatly to be desired.’ At a later point—was it days later? Or weeks, or months?—he returned to the mountain and came down, abashed, to state that he had been deceived on his previous visit; the Devil had appeared to him in the guise of the archangel, and the verses he had been given were therefore not divine, but satanic, and should be expunged from the Quran at once. The angel had, on this occasion, brought new verses from God, which were to replace the satanic verses in the great book: ‘Have you heard of al-Lat and al-Uzza, and al-Manat, the third, the other one? They are but names that your forefathers invented, and there is no truth in them. Shall God have daughters while you have sons? That would be an unjust division.’ And in this way the Recitation was purified of the Devil’s work. But the questions remained: why did Muhammad initially accept the first, ‘false’ revelation as true? And what happened in Mecca in the period between the two revelations, satanic and angelic?
Salman Rushdie (2012). Joseph Anton: A Memoir, pp. 38–44. London: Vintage.
Based on this, we can be confident that Rushdie was aware of the historical context, and had a historian’s skeptical position on the reliability of the sources. Most likely, Rushdie says, there was some historical incident behind the episode of the satanic verses, even if the sources don’t give us any confidence what it was. Rushdie speculated (pp. 44–45) that the episode may have represented a rapprochement between Muhammad and the powers of Mecca (who collected tribute in the names of the three goddesses) followed by a split. But he also saw the episode as possible inspiration for fiction:
Good story, he thought when he read about it. Even then he was dreaming of being a writer, and he filed the good story away in the back of his mind for future consideration. Twenty years later he would find out exactly how good a story it was.
Rushdie, p. 45.