Why Did Charles Dickens write A Christmas Carol?

Money might have been a big factor.

See The Writer's Almanac with Garrison Keillor. Excerpt:

"It was on this day in 1843 (Dec. 19) that Charles Dickens published A Christmas Carol. Dickens wrote the novel after his first commercial failure. His previous novel, Martin Chuzzlewit (1842) had flopped, and he was suddenly strapped for cash. Martin Chuzzlewit had been satirical and pessimistic, and Dickens thought he might be more successful if he wrote a heartwarming tale with a holiday theme.

He got the idea for the book in late October of 1843, the story of the heartless Ebenezer Scrooge, who has so little Christmas spirit that he wants his assistant Bob Cratchit to work on Christmas Day.

Dickens struggled to finish the book in time for Christmas. He no longer had a publisher so he published the book himself, ordering illustrations, gilt-edged pages and a lavish red bound cover. He priced the book at a mere 5 shillings, in hopes of making it affordable to everyone. It was released within a week of Christmas and was a huge success, selling six thousand copies the first few days, and the demand was so great that it quickly went to second and third editions.

At the time, Christmas was on the decline and not celebrated much. England was in the midst of an Industrial Revolution and most people were incredibly poor, having to work as much as 16 hour days, 6 days a week. Most people couldn't afford to celebrate Christmas, and Puritans believed it was a sin to do so. They felt that celebrating Christmas too extravagantly would be an insult to Christ. The famous American preacher Henry Ward Beecher said that Christmas was a "foreign day" and he wouldn't even recognize it.

When Dickens's novel became a huge bestseller in both the United States and England, A Christmas Carol reminded many people of the old Christmas traditions that had been dying out since the beginning of the Industrial Revolution, of cooking a feast, spending time with family, and spreading warmth and cheer. Dickens helped people return to the old ways of Christmas. He went on to write a Christmas story every year, but none endured as well as A Christmas Carol."