Most aren't generals, but most want to be generals, or at least Colonels/Captains.
The vast majority are officers returning from overseas assignments who are being reassigned to teach ROTC. They are being given basic lesson plans and educational material to present to college ROTC students. They are being taught how to grade papers and use the teacher's edition of text books.
Where did you get that notion? I never attended a War College, but I did do Squadron Officers School, which is the first step of the Air Forces Proffessional Military Education ladder. It's followed by the Air Command and Staff and Air War College. Several of my compatriots were doing AWC by correspondence, and I assure you they didn't study lesson plans, nor did they discuss the best ways to produce new butter bars at their seminars.