I asked a born again Christian what a cult was when I was a teenager. He said a cult is where people worship a man as though he was God.
I silently filled in the next sentence in my head: "...but Christianity isn't a cult, because Jesus really was God..."
Which is not to claim that Christianity is exactly the same as all the cults it won out over...but the differences can't be nearly as obvious as they seem in hindsight.
In every cult I know of, the worshipped man is physically present to benefit from the worship and control the followers.
Christianity didn't really have that, ever, even if you take the Gospels as sober, rigorous history. They claim that Jesus ascended to heaven a few weeks after his resurrection.
So, I think that's actually a significant differentiator.
During the time of a polytheistic roman empire, Christianity was literally a cult, and an underground one at that. Judaism and the Roman pantheon had more adherents. Outside of the Roman controlled spaces, Zoroastrianism certainly did, as would Hindu and Buddhist faiths. Probably more Celtic believers.
The transition from cult to state church must have been tremendously affirming for some, but probably accepted with resignation by as many, for some time.
There are still plenty of Christians who rue the transition to state church, although they tend to be in the minority. You'll usually find them in the fringes in things like the Catholic Workers or the New Monasticism (which is sort of a protestant Catholic Worker movement). I'd assume that many Quakers also fit the mold.
Quakers break the mould in more ways: they include the small subset of athiest quakers. Well, let's be polite. Nontheist.
A charming church of scotland minister in fife told my athiest brother it was no barrier to a successful career in the church, one should not allow a trivial obsession with the 39 articles to stand in the way. He specialised in computer aided stylometry of amongst other writing, the Pauline epistles.
There was a bit of a public debate a few years ago (maybe more than a few years ago) whether belief in God was necessary for Unitarianism. IIRC, there was a smallish schism as a result of the debate between the deists and atheists.
From the little that I know of Quakerism, I would think that at least some level of deism would be necessary, but who knows.
Graham Greene had a short story, “The Last Word,” (the title story of his final story collection) which posited a world in which atheism had become nearly universal and the military dictator summoned the last believer, the Pope who had become senile with age to assassinate him. After shooting him, he began to have doubts about his atheism and faith continued.
The rise of Islam was even more tremendous, beginning in Muhammad's 40th year when the archangel Gabriel first began communicating the Quran to him, and becoming the largest religion in Arabia by the time of Muhammad's death 22 years later.
Every cult is also gnostic, e.g. they attract people who want to learn their secrets so they can be a part of the insiders.
Christianity was unique when the founder said that it was for the gentiles (everyone) and that meant it should spread everywhere (that’s actually where the word ’catholic’ or ‘universal’ comes from).
I'd agree on paper. I'd say it's clear the reigns of English are firmly in control by what happens in the USA. And Spanish is likely at the point, due partly to its rise in importance as it increases usage in the US, leading to Mexico being the world's canonical source for Spanish. You couldn't tell an Englishman or Spaniard this, but I'd bet most international students aren't looking to emulate how they speak in England or Spain, but rather the US, Mexico or Columbia. As a second language speak of Spanish myself, I know I would greatly prefer to blend in more in Latin America than in Spain. It's just a larger part of the world.
Ultimately the US was founded by English speaking people, just as Mexico was by Spanish speaking people. These languages are as much ours as they are Europe's. But we both definitely dictate the ultimate future of both languages now out of sheer numbers and economic influence.
I silently filled in the next sentence in my head: "...but Christianity isn't a cult, because Jesus really was God..."
Which is not to claim that Christianity is exactly the same as all the cults it won out over...but the differences can't be nearly as obvious as they seem in hindsight.