Read up on Rhodesia, and more broadly the anti-colonial struggles in Africa. Africans weren't even second class citizens: the vast majority were given zero say in governance. Legal protections were de facto non-existent. And, in the midst of the bush war, tens of thousands of civilians were killed by the Rhodesian military.
Does that at all excuse Mugabe post-Rhodesia? Not at all. But it's important to contextualize him if you want to understand why many still valorize him.
As a point of comparison, Americans celebrate George Washington for leading a successful anti-colonial struggle and establishing a republic. But, a much darker gloss is that he founded a white settler republic that enshrined a brutal system of slavery in its Constitution and that regularly committed campaigns of genocide against non-dominant ethnic groups. Indeed, British restrictions on that was a substantial motivating factor for the white American settlers to have rebelled.
Reducing Washington to that would mislead more than it reveals, but people are doing the exact same thing with Mugabe. Focusing on Mugabe's very real sins to the extent it obscures what people find compelling about him is limiting your own understanding of the world.