I think it is economic strategy, although I am not a supporter of the Venezuelan government, or the ANC (I am South African). I can see the possible economic benefits South Africa could get from Venezuela. Our president is a strategic businessman, and I don't doubt his experience in that regard. He was very influential in forming workers Unions in the Apartheid days, and thus came a predominant "struggle" leader, among others. I just think he is not as good as politics as he is at business. I could be very wrong but being friends with Venezuela as it is now, could earn us brownie points with them, considering how the rest of the world is alienating the current government. As far as I am aware Venezuela has the largest oil deposits in the world? (they do...) The left in South Africa has a historic "comradeship" with socialist from Latin America, in particular, Cuba, who now are helping us fight COVOID-19. They also assisted MK in old bush wars. I think it's more of a historic bond, one which could pay off. Who knows, I do know the ANC greatly admired Hugo Chávez, and his economic policies. The newer generation of socialists in our country do support, and are inspired by the Revolutionary Bolivarian Movement. The EFF for example, were great supporters of that particular movement, and often praised it publicly.
To me it a logical decision to make, because it does seem to appease both the majority poor, as well as rich minority. We have a funny form of democracy in our country, it goes in and out of socialism and democracy, called it a "mixed" economy, of both a private sector, and SOE's. I don't think South Africa wants trouble with anyone, but I think the ANC know the leverage they hold, and how South Africa keeps Africa relatively stable (as can be), our geo-political, as well economic position in the South Atlantic is kinda an underrated security net as well, it's like a buffer between the Western and Eastern hemispheres . After all it is true when they say that South Africa is the gateway to Africa.
Talking about Russian and Chinese interest in our country, to me it is also logical for them to take interest in South Africa, and the potential of what an alliance between our country and the Venezuelan government as it is, or what it may become,can achieve. Both countries are in need to develop their infrastructure to fully make the most of their resources, so it's logical, business. Russia and China, if they get it right, they stand a chance to gain a strong foothold in both Africa and South America, and probably among socialists governments in Latin America.