Not surprisingly he seems to be conflating issues.
https://www.cbsnews.com/news/south-afri ... ure-tweet/
Earlier this month, Ramaphosa announced that the policy of his party, Nelson Mandela's African National Congress (ANC), was to look at changing the constitution in order to allow for land expropriation without compensation and would proceed with plans carry out that change.
That being said I can understand the locals fear as violent farm seizure is basically what happened in Zimbabwe.South Africa has high rates of violent crime, Patta reports, but there has been a well-funded campaign by white right-wing South Africans to promote the idea that white farmers are being deliberately killed at higher rates than people of other skin colors, and that this constitutes a "white genocide."
I'd ask why Trump felt to need to tweet this but that would be a waste of time.