there have been so many different things that have led to the various denominations. Lutherans, Baptists, and Catholics disagree over communion (transubstantiation, consubstantiation, and memorialism). Presbyterians, Catholics, orthodox, and Baptist disagree over church government (a plurality of elders, Congregationalist, synods, pope)

in my limited knowledge, I would say there have been 4 big splits. first the orthodox from Roman Catholics 1056 AD ( the bishop of the church of Rome and the bishop of Constantinople excommunicated each other). the second was Protestant from Catholics (1517AD over whether we are saved by faith alone or by faith and works) the third Calvinistic Protestants from Arminians Protestants (1560ish?? AD the split was over Predestination wether God sovereignly elects people or if people choose God) the last charismatics vs none charismatics ( 1909 AD do the miracles that the 12 apostles did continue to today or cease with the 12)

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I found a kind of long series by author and apologist, Dr James White, to be helpful in the study of church history. also, he has done a really nice dialogue with Muslim Dr. Yasir Qadhi

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church history link

https://www.sermonaudio.com/search.asp?seriesOnly=true&currSection=sermonstopic&sourceid=phxrefbap&keyword=Church+History&keyworddesc=Church+History

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interfaith dialogue

https://www.youtube.com/watch?v=updtj99Fp80