Due to the fact that he no longer loves her, and that he has an unreasonable love towards money instead.
Belle was Ebenezers betrothed. She saw that a golden idle had taken her place in his heart and released him from his promise of marridge
Belle had seen that the Young Scrooge had another idle in his heart - money
There isn't a time frame indicated in the original story but as Scrooge is still quite young and he is working for himself its assumed circa two years
The other young apprentice at Fezziwig's warehouse where the young Scrooge worked was Dick Wilkins. He was a friendly and cheerful colleague of Scrooge, who later went on to become successful and prosperous.
he played the young scrooge and tiny Tim
George Cole played the young Ebenezer Scrooge. Who went on to star with Sim in other films notably The Saint Trinians sargas
When Pimple Was Young His First Sweetheart - 1914 is rated/received certificates of: UK:U
Scrooge McDuck voiced by Alan Young
Scrooge worked for Fezziwig when he was young, but his business partner was Jacob Marley.
Fezziwig was Scrooge's boss who was very kind and generous.
According to his sister who comes to him at the school, Scrooge's father is quite abusive. We can only imagine what relief it is for Scrooge to have the relative peace and tranquility of the school as refuge. Perhaps his father realizes what a terrible home he has made for young Scrooge and is attempting to give him a better environment.
The name of Scrooge's fiancee was Belle -- he never married. They apparently became engaged while Ebenezer was an apprentice at Fezziwig, and maintained their engagement over his early years of acquiring wealth. However, she broke their engagement after she realized that Scrooge loved money than he loved her. Belle asked the young Ebenezer point blank whether he would want her as a wife now, knowing that he would get no dowry money for doing so. Ebenezer chose not to say he would do so, which was (unfortunately) the honest answer.