Christmas used to be a very church-centered holiday. The observance of it was falling at the end fo the 18th century / beginning of the 19th century.
However, Charles Dickens' "A Christmas Carol" would change the way Christmas is celebrated up to this day. The main shift that occurred due to Dicken's work is from a church-centric celebration to a self-centered generosity festival.
The story of Scrooge changing his mind and helping out his workers moved people into celebrating Christmas as a time for being generous, being around loved ones and helping people out. This shift resulted in the more typical celebration of today, where families get together and celebrate by eating.
He also helped propagate emerging traditions such as gift-giving and the display of Christmas trees, which had been introduced by Prince Albert but were not ingrained into the public consciousness until Dicken's work became popular.
As a last note, while some of these traditions had in some form existed before, they were dwindling and were repopularized by Dickens. There's a lot more on this subject to read, so check out the sources!