Can't speak for the other places, but I traveled in Tanzania in the 1980s, under Nyerere. One newspaper in the whole country, put out by the state. Comical roads with potholes big enough to store a Volkswagen. And few of those. Secret police lounging around Dar-es-Salaam. Corruption absolutely everywhere.
But they were a "front-line state" against South Africa. I'm not endorsing South Africa, but sheesh! Black or white, people preferred it to Tanzania. If not for the Soviet interest and the racial obsession in the West, the country would have made a transition like Chile. Instead, it's headed down the tubes.
I believe the government was better in the 1960s and 1970s.
What evidence do you have that people preferred South Africa to Tanzania?
The comparison to Chile is a counterfactual one. It would be nice if we could say that such a transition would have happened, but there is no way to prove that such a transition would have happened.