John, I agree with you in all except one point.

Constantine, an upper class roman soldier and son of emperor Flavius Valerius Constantius, was stationed in Eboracum (i.e., York, in England) in the year 306, when he learned that his father died. He declared himself an emperor and sent message to Rome saying, "piss off, I take the throne". The throne suitors were not happy, so he fought hard against them and won. On paper, he was Roman Emperor from 306 to 337, but, in reality, it's only in 324 that he was emperor without rivals.

In 313, while he was still fighting for being the sole emperor, he decriminalized Christianity. The reason was, most likely, political: he wanted to get on his side the Christians who were becoming a majority. Like a modern politician, he wanted to be good to the masses.

In 325, that is, a year after he became the sole Emperor, he wanted to create greater unity among Christians who were comprised of many factions, disagreeing about core aspects of their faith. So he called a meeting, known as the First Council of Nicaea, where he and theologians decided what people should believe in. This council became the foundation of the Christian faith.

Where I disagree with you is that the establishment of Christianity, by Constantine, in 324, was not called Catholic. It was, simply, Christianity.

Now, as known, Constantine, having to rule a vast empire, established a second capital in a small town called Byzantium, at the border between Europe and Asia. He changed its name and called it Constantinople (i.e. the city of Constantine). The part of the Roman Empire administered by the second capital became known by the old name of its capital, i.e., Byzantium and, little by little, it split into a separate kingdom/empire, comprising mostly of Romans speaking Greek. Thus, the eastern part of the Empire, Byzantium, adopted Greek as its official language some 200 years after Constantine.

As was unavoidable, the Empires split while maintaining the same religion. But, in 1054, they started debating about some aspects of their faith and this led to the splitting of the religion too. The Western part of the Roman Empire (under Rome) adopted the name "Catholic Christianity", meaning "Universal Christianity", just a name they invented to make the others jealous. The Eastern part of the empire, which was, by now, a separate empire, Byzantium, used the name "Orthodox Christianity", i.e. the Right Faith Christianity.

This is the origin of Catholicism. It began in the 11th c.

Religion is, of course, an invention of men (men, mostly, not women), and, certainly, it is used by states to control people (e.g. nobody in the US can become president without pretending they read the bible or go to church), to perform financial transactions, to cheat, to murder, but, often too, to do some good things. However, any system invented by people has its bad and good sides. Certainly, religion is a bad idea, a very primitive system for creating societal cohesion, but it is with us, and it'll take long time before we rid of it. And, at this stage, I hope that state religion will not replace supernatural religion, because I don't know what is worse.

Meanwhile, wishes like "happy easter" are used by most as a metaphor for saying "wish you a good spring" and most are happy in never investigating why they say "happy easter", why they circulate eggs and bunnies, etc. It's just something that people do, for no reason other than creating some mutual form of communicating good wishes.

you are very welcome, Maxxie!