Esq, that doesn't necessarily mean that Allah was always equated with Yahweh. Allah could well have a pre-existing deity that was conflated with Yahweh in order to maintain cultural beliefs, practices and identity whilst adopting a new religion. After all, assimilation has long been one of christianity's greatest tools and I doubt they are the only faith to have used it.
(cue jokes about religious tools)
(cue jokes about religious tools)