Some facts you may not have known about St. Patrick:
St. Patrick was not Irish. He was a British Celt, first enslaved in Ireland as a teen. He was later a missionary to Ireland after converting to Christianity. He was not an Italian but was a Roman citizen. So technically the most Irish of holidays is named after an English guy (oh the irony).
St. Patrick was also not necessarily the first Christian missionary to Ireland.
No one knows the day Patrick was born or the day that he died. March 17th is traditionally considered to be one of the two but there is no documentation to support this.
The only documents about Patrick are his Confession and a letter he wrote to some guy named Coroticus.
There were never any snakes or other reptiles in Ireland for Patrick to chase out. That's a myth.
Patrick predates the Roman Catholic Church, and was considered a "saint" (or holy man) before the Roman church created its canon (list) of saints. They then added him to it.