Christianity is a joke...underground heretic bible study type flex for slaves until Emperor Constantine hijacked it. For the first hundred years, look at the saints/martyrs...all nobodies. Then later, high quality/scholarly ppl adopted it like St Augustine. Islam was adopted by every class from inception, the slaves and the noblemen. It did not need some "person" in political power adopting it for it to grow.
Israelites/yahoodis are closer to the truth, they got punished, lost their temple and got scattered for their killings of prophets and other arrogant acts, but the Israelites/Hebrews /Jewish ppl atleast didn't become a thing because some Roman tyrant decided to adopt their beliefs, and then fuse Greco-Roman pagan shit like the Trinity and other blasphemous additions (bid'a in Islam, huge sin)
Without Emperor Constantine, no Christianity, no ecumenical councils, no Papacy, no crusades, no reconquista, no forcing Mudejars, Jews, Filipinos, Africans, Indians and South Americans etc convert by force it would just be an inferior version of Chabad Lubovic or the millions other Jewwy cults.