I thought Obama considered Afghanistan a war of necessity. Why the dithering?

Because running a war is a lot harder than running your mouth, it requires intelligence, and courage, brains and guts, a better strategy than just blaming the previous administration. He can't say we seek victory, he can't admit what the enemy we face is, he wants to please Putin, who wants the USA to be as humiliated in Afghanistan as the USSR was, and is only isting our presence there so they (the Kremlin) can ist the enemy in attacking our troops. IF they withdraw all the troops from Afghanistan, you can bet they will just be redeployed somewhere like Yemen, Sudan, etc., maybe even helping to restore the Honduras dictator to office, which seems dear to Obama's heart.