Alright. A TL;DR version of their history is simply you had many religions such as versions of, Christianity, Judaism, (and lots of polytheism) Manafism, Aglibolism, Athtarism (most of these deity were kept at the Kaaba, which is now a very sacred Islamic shrine supposedly built by Abraham), etc…then Mahammad gained support because he was kinda well off, but did something provocative and started taking care of the poor, because he gave them gifts and spoke populist rhetoric. Once he gained power, he was kicked out of Mecca, was taken in by the powers of Medina, Medina became his power base, war between Mecca and Medina, before Muhamad eventually conquered Mecca with his army on their doorstep, they all, the leaders of mecca, in mass exodus, joined Muhamad, thus creating the first Islamic State. Then Muhamad died....
Giving rise to the first four Caliphs, Abu Bakr, Umar, Uthman, and 'Ali, which finally united the Arabian Peninsula, then began conquering territory from the two main regional superpowers, the Persian and Byzantine empires. Once conquered they largely let local communities govern and practice their religion as they had been, because, and this is very telling, if you look at where the Arabian Peninsula is located, it is directly on a superhighway for trade, which long before Islam shaped Semite people (Arabs and Jews) into what they really are, businessmen, which is why when they conquered they didn’t care what religion somebody was, they just wanted money lol.
^Supposedly this reply couldn't fit into a comment. :/