In school we learned that when Christianity emerged it had novelties that appealed to the common people and helped it spread. E.g. the Roman and Greek religions perceived the gods as wicked, at times cruel and selfish, and people have to subdue to that like they have to subdue to the kings/aristocracy. On the other hand Christianity claimed that nobody should be cruel, God is not cruel either, and for the good people there will be afterlife in heaven. This appealed to the common people and facilitated conversion. Other examples of theological revolutions/novelties pleasing the common person are "whoever is free of sin throw the first stone" (I should be forgiven), "if you have 2 shirts give one to your neighbour" (I am poor and deserve solidarity), "the last will be first" (There will be divine justice).
My question: what were novelties of early Islam compared to Christianity, Judaism and other religions that helped Islam spread?