Patrick wasn't particularly religious until after he was kidnapped and sent to Ireland to raise sheep. He heard voices that urged him to escape his captors. He escaped but later was captured, again, and sent to be a slave in France!
Patrick spent many years in France and became a bishop there.
Patrick became a missionary and that is when he returned to Ireland.
Patrick did not like particularly like green. He was usually dressed in blue!
Patrick did promote the shamrock as a religious symbol (of the Holy Trinity).
Patrick did not celebrate with corned beef! Irish immigrants to this country began brining beef brisket because it was cheap!
It does appear that our celebrations are historically accurate on this point: Patrick enjoyed a drink or two!