As with most of the other disasters of the 20th century, we can blame the British Colonial Service for the current state of Zimbabwe.
Kissinger, for all his numerous other failings, was a hardnosed practicalist, and had Ian Smith on the verge of a settlement for enfranchisement of the Rhodesian majority when the Foreign Office interfered because all parties in the discussions preferred the negotiated timetable over their expedited version.
ZANU, as the most potent organization for black nationalism, swept the elections, and there's been decades of Robert Mugabe ever since.