Complex sentence: Softkey faced many financial adversities in the late 1980's due to competition from other software companies, but continued to prosper throughout the 1990's, when O'Leary became an aggressive promoter of the company's products.
Split into simpler sentences: Softkey faced many financial adversities in the late 1980's due to competition from other software companies, but continued to prosper throughout the 1990's under O'Leary's leadership. When O'Leary became an aggressive promoter of the company's products.