I'm not entirely sure what I'm supposed to glean from those links. It's true that the current president of Botswana is the son of the first president, but Botswana is hardly alone in this kind of dynastic succession. I can name a few first-world democracies where multiple members of the same family have been elected heads of state.

And yes, Botswana is overly dependent on the diamond trade, and De Beers is a very shady company. The forced relocation of the San bushmen was an atrocity. Also, the country has a huge HIV/AIDS epidemic. But I wasn't holding up Botswana as a shining exemplar of all that is good in this world. I was saying that it is, overall, a much better place to live in than it was before independence. Do you disagree?

Note what Namibia and Botswana have in common besides being nice places to live in Africa and being considered "liberal democracies". Note where they tend to land on this list and how their economies tend to be strongly tied to resource extraction.

Zimbabwe also has a low population density and an economy strongly tied to resource extraction, so those two factors by themselves don't fully account for the relative prosperity of Botswana and Namibia.