Pre-Islamic Arabian religion is known from inscriptions, from poetry, and from Muslim writers describing what was replaced, so it is reported chiefly by people with a case to make. What emerges is a body of local deities, among them Allat, Al-Uzza and Manat, worshipped at particular sanctuaries, alongside a high god whom the Quran assumes its audience already acknowledges. Sanctuaries were served by custodian families, pilgrimage and sacred months already existed, and the Kaaba at Mecca was one shrine among several before it became the only one.
The jinn belong to the same world and did not leave it. Amira El-Zein's study traces them from pre-Islamic poetry, where a poet's inspiration could be attributed to a familiar spirit, into the Quran, which affirms their existence as a created order with free will, obliged as humans are and capable of belief or unbelief. That continuity is why the jinn are a doctrinal category rather than a folk survival.
Divination by arrows, the reading of birds and the consultation of the kahin, a seer speaking in rhymed prose, were the ordinary religious techniques. The Quran's insistence that Muhammad is neither a kahin nor a poet is a response to the categories his first hearers already had available to them.