Why did Charlie Chaplin leave Keystone Studios for Essanay Studios?

Charlie Chaplin left Mack Sennett’s Keystone Studios in 1915 to accept a more lucrative contract at Essanay Studios, which offered him $1,250 per week.1

While his time at Keystone served as the gestation period for his iconic Little Tramp character, his move to Essanay allowed him to further develop his craft. At his new studio, Chaplin began to incorporate elements of pathos into his comedy, notably in films such as The Tramp (1915) and Burlesque on Carmen (1915).1