Meh.
I think the use of the MOAB weapon was equal parts testing it out, having some "fun" with a big ass bomb on some assholes who seriously deserved it, and sending a message to anyone who feels that a demonstration of our might and prowess is relevant to them and their interests. An All Points Bulletin of sorts to say, "Hey check this out... we've still got toys we haven't even popped on scumbags yet. Remember us?"
As for Afghanistan, other than keeping ISIS, ISIS-K, SPECTRE, Hydra, HIVE, and any other miscreant organizations suppressed, who really thinks we have an end-game there that includes a stable democracy and a McDonald's on every street corner? That's never going to happen.
The best we can hope for is that Al Qaeda, ISIS and the Legion of Doom are either wiped out or kept at bay, and the rest of the country somewhat peacefully goes back to the caveman #### they've been doing for eons. Stuff like growing poppies for opium, screwing goats, subjugating their women, and dressing up little boys to look like little girls so they can screw them instead of goats.
Come to think of it, we should probably just rescue all of the women, children and goats, and then nuke the whole goddamn place. We haven't used one of those boomsticks lately either and the world kind of needs THAT reminder too.