Answer:
The answer is to engage the audience.
Step-by-step explanation:
In the reading of the lesson, they specifically state the reason in the following paragraph;
Authors often write fiction about historical characters to address a specific audience. Who was Miller’s audience at the time, and why did he feel the need to change Abigail’s age? Audiences need to relate to a storyline, too, and authors need to keep them interested and reading. The Crucible is an important documentation of American history, and it's a testament to how history often repeats itself. A young girl of eleven or twelve is now legally considered a minor and too young to consent to a relationship with an adult.
Had Arthur Miller stuck to these facts, he’d have risked taking attention away from the storyline and bringing more attention to the moral issues of John Proctor, with less empathy for his already flawed character.