How is Scrooge a changed man at the end of A Christmas Carol?
Scrooge learns his lessons from the three spirits who visit him during the night. He recognizes that he may suffer the same fate as his former partner, Marley, so he decides to change his strict business ways. His days of being the most miserly man in London are over, and he demonstrates this by buying the giant prize turkey and anonymously sending it to the Cratchits, handsomely rewarding the young boy who fetches it for him. After having turned down the men who requested a charitable donation on Christmas Eve, he locates them on Christmas morning and promises them a huge sum of money. Having ridiculed and insulted his nephew a day earlier, Scrooge decides to pay him a visit on Christmas and make amends for his lifetime of hard-hearted disinterest. Instead of growling "Bah, humbug" to people on the street, he greets them with a "delighted smile" and a "Merry Christmas to you." As for Bob Cratchit, Scrooge sees how badly he has mistreated his loyal worker, and promises Bob a huge raise--and a financial hand in seeking adequate medical treatment for Tiny Tim.
Scrooge was better than his word. He did it all, and infinitely more; and to Tiny Tim, who did NOT die, he was a second father. He became as good a friend, as good a master, and as good a man, as the good old city knew...
... and it was always said of him, that he knew how to keep Christmas well, if any man alive possessed the knowledge.
The visits from the three spirits were meant to help to redeem Scrooge. The purpose of the visits is to help Scrooge change from an angry, lonely miserly man to someone who embraces people and shares his wealth to make the world a better place. The whole point is for Scrooge to stop worshiping money, and to realize that love, family, and friends make life rich, not money. He has money, yet he is very poor.
The Ghost of Christmas Past brings Scrooge back to a time when he was young and interested in enjoying life. This spirit shows him he is so lonely because of the choice he made to surrender his heart to the pursuit of money. He systematically cut himself off from the people he loved.
The Ghost of Christmas Present brings Scrooge into the homes of Bob Cratchit and his nephew Fred to show him how people join together and celebrate. The Cratchits are poor, but they have a family that is happy and loving. Fred married a woman he loved and he too is very happy.
The Ghost of Christmas Yet to Come is sent to show Scrooge that his death will come one day too and without making any human connections in life no one will mourn his passing. No one will care when he dies, because he did not care about anyone when he lived.
The spirits or ghosts that visit Scrooge are solely responsible for the reversal of his life perception. First, the ghost of his old partner, Marley, comes to give him a general warning about his greedy and miserly ways. Scrooge takes his words to heart somewhat, but the other three ghosts are truly responsible for his turnaround.
The ghosts of Christmas past, present, and future give Scrooge a feel for the generosity of Christmas in all its forms. Whether it's his recollections of childhood (past), an understanding of how others celebrate (present), or the impending sense that he one day will die a lonely and isolated death if he continues his current course (future), the three ghosts inspire Scrooge to change his ways.