His nickname is actually "Chaos", from his time as an operational commander.  "Mad Dog" was a media invention that neither he nor his troops thought much of.  
The Trump administration is a disaster but it isn't particularly the Sec Def's role to become embroiled in current crises, he manages DOD and provides the resources for policy makers. It's McMaster at NSC (thank God they got Bannon out of there) and the Joint Chiefs who provide current military policy advice.  
The first thing they would have asked is what is the effect or end-state to be achieved? Was probably met with resounding silence from the oval office and an order to just hit something. It gave the buffoon's dismal polling numbers a bump. 
If you think Mattis is simple, one-dimensional or uneducated, I'd suggest a little more review before commenting. 
Not sure why you take issue with bombs in Afghanistan, we dropped plenty of ordnance there ourselves.