Why a Comic Book
Because they're really cool - and the US Government has been using them for years.
Comic books are just plain cool. Also, the U.S. government has produced comic books to help train their soldiers on difficult tasks, written a comic book about assimilating back to civilian life and more.
The reader can recall words verbatim.
Ever had an interaction and wished you had handled it differently? As you begin to think over your interaction you come up with the best way you wished you had responded. When we read comic books we remember and recall information verbatim. Next time someone says or does something inappropriate you may not know exactly what you want to say - but you'll have a few new ideas to help you out.
The reader connects emotionally with the characters.
One of the reasons why Define the Line comes in a printed format is because when we hold a physical book we connect emotionally with characters. If that's not magical than we don't know what is.
Learning happens at the reader's own pace.
When it comes to learning - we all are different from one another. If we provide individuals with video training - it's likely that many of them will miss important information because the pacing isn't right (it could also be because they're on social media instead of paying attention - but that's a whole other issue). Having a printed comic book that employees can keep in their desk, reference when needed, and have as an ongoing tool makes learning easier to digest and can be done at their own place.