“He was helpful in establishing a legitimate government in Afghanistan after the Taliban fell. That will be his legacy.”
Despite himself.
He wanted to be king - the loya jirga said no.
He played a purely ceremonial role.
That reminds me of an article I posted here a few months before 9/11 -
U.S plans to impose Zahir Shah on Afghans: Hekmatyar
And he did serve briefly as Afghanistan's interim leader before Karzai took office.