Why did Christianity spread so quickly?

Actually, it didn't.

Until Constantine made it the official religion of the Roman Empire (which fell shortly afterward), it was very much a minority group of scattered sects with differing beliefs around the middle east. No leader of the Northern Europeans accepted it until Clovis (King of the Franks) did in the 400s, and it wasn't widespread in Europe as any kind of accepted or "official" religion until well into the 700's and 800's.

Once it was accepted by the scattered kings of Europe, though, as the imposed state religion people had little or no choice about their religion.

You could really benefit from reading some history.

Peace.

"Only" 300 years? You realise that even after Constantine converted, the majority of Roman citizens still weren't Christian, right?

Christianity spread very, very slowly - the last people in Europe to convert to Christianity didn't get around to it until the 1800's.

Islam spread very quickly though.

And yes, it was just power - Christianity was spread mainly at the end of a sword. Look up Charlemagne's conversion of the Saxons for a top example of this.

Because the disciples of Christ were very zealous to carry out his instructions that he gave them before he ascended to heaven about making disciples: (Matthew 24:14) And this good news of the kingdom will be preached in all the inhabited earth for a witness to all the nations; and then the end will come. (Matthew 28:19-20) Go therefore and make disciples of people of all the nations, baptizing them in the name of the Father and of the Son and of the holy spirit, 20 teaching them to observe all the things I have commanded YOU. And, look! I am with YOU all the days until the conclusion of the system of things.” (Acts 1:8) but YOU will receive power when the holy spirit arrives upon YOU, and YOU will be witnesses of me both in Jerusalem and in all Ju·de′a and Sa·mar′i·a and to the most distant part of the earth.”

Heretics assent neither to Scripture nor to tradition"

JEROME

"Do you demand Scripture proof? You may find it in Acts of the Apostles. And even if it did NOT REST on the authority of the Scripture the CONSENSUS of the WHOLE WORLD in this respect would have the force of COMMAND..." C. Dialogue Luciferians 8

"And let them not flatter you themselves if they think they have Scripture authority since the devil himself has quoted Scripture texts...we could all, while preserving in the letter of Scripture, read into it some novel doctrine"

"We do not take our scriptural teaching from the parables but we interpret the parables according to our TEACHING" Purity 9,1

"Let them show the origins of their churches, let them unroll the list of their Bishops (showing) through a succession coming down from the very beginning that their first Bishop had his authority and predecessor someone from among the number of Apostles or apostolic men and, further, that he did not stray from the Apostles. In this way the apostolic churches present their earliest records. The church of Smyrna, for example, records that Polycarp was named by John; the Romans, that Clement was ordained by Peter. In just the same way, the other churches show who were made Bishops by the Apostles and who transmitted the apostolic seed to them. Let the heretics invent something like that" De praescr haeret 32

Roads my dear; Roman roads! Also, Christianity affirmed human dignity in a world where the person was often dehumanized! It only required repentance from sin and belief in the grace of Jesus Christ to save.

In short, Christians were conquerors.

They took over everything, killed just about everybody, and set up shop.

They spread so fast because they were very imperialist-minded.

Check anywhere in the world where Christianity is, chances are it's because it had been attacked and colonized by Christians at some point.

How did Hitler convince a whole country to kill of a bunch of human beings in the most terrible way possible?

the roman empire was full of trade, they had the most effective system of roads during the ancient world... ideas spread quickly... especially christianity which was popular with the lower classes... and eventually the roman emperors were forced to adopt it...

Beause jesus christ is so powerfull and people love knowing he is there to protect us if we share the word of god with the people around us he would be happy when all good go to heaven

listen to the song: untill the whole world hears by: casting crowns

The Black Plague gave them a head start; they killed the rest of the competition themselves.