Flexibility in how memory was handled.
The Official OOP Guide (now a cult classic among retro-coders) famously told users to "strive to forget what people have told you about OOP" and just sit down and try it. 2. The Language Evolution Turbo Pascal 5.5 Object Oriented Programming Guide
Before version 5.5, Turbo Pascal was the undisputed king of MS-DOS because of its speed—it could compile programs in seconds that took other compilers an hour. When version 5.5 arrived, it brought to the masses. For many developers, this was their first real exposure to concepts like classes, inheritance, and polymorphism. Flexibility in how memory was handled