Collecting gun-related injury and fatality data allows us to make evidence-based informed decisions about what types of legislation are likely to be effective to reduce harm. For example:
And that has nothing to do with Disease Control and is a clear demonstration of mission creep. The CDC has recently displayed its incompetence regarding its core function. Maybe it should master that before addressing other issues of society which are, at best, only tenuously in its purview.
You have many questions. At first it seemed as if you were curious about what other aspects the CDC had delved into. Now it looks like you are pursuing some agenda. The basic questions can be answered with a bit of research. Here are some more to ponder. Or maybe these are what you are getting at.
What was the CDC's original mission?
Did it execute it competently?
Why is it now involved in areas other than communicable diseases?
Do people in organizations seek to increase their power and influence?
Do they do this by enlarging the scope of their organizations' missions?
How is this notionally science-based entity being influenced by other factors?
I actually suspect this role was thrust on the CDC because they are generally supported by everyone (everyone sane anyway). I'm not a fan of this having happened because they should be too important to get mixed into politically poisonous debates.