As a Christian, I’ve always maintained that Islam is a devilish imitation of the Pharisaic Judaism that so opposed Jesus and the first generation Church.
Way before AD 630 the pagan/polytheistic religions were collapsing all over—at first voluntarily, and later with the aid of Roman culture—in the face of Christianity. The one religion which didn’t change though was the monotheistic law-based Judaism which opposed Jesus... Judaism though, then as now, was a small minority religion, without any aspirations to evangelism—and largely ethnically based.
Therefore, WHAM! Comes developed a new monotheistic law based religion, spread evangelically by military conquest/sharia law....without the essential ethnic basis like Judaism. It has its own holy books....which claim Judaism and Christianity totally corrupted the bible, and got everything wrong, which it finally set right... It fundamentally appeals to human pride and the predilection to warfare..... A cheap ripoff of Judaism (with a large measure of Arab superstitions/traditions, and a dash of Christian ideas thrown in the pot...)
Of course I don’t mean to be offensive to Judaism—which I consider true, as far as it goes. As a Christian though, I do think, as the New Testament teaches, that they missed the Messiah, Jesus,...as of course, does Islam.