It is really sad to see the retirement of cricketers from South Africa and West Indies. There are many cricketers who retire from their country's cricket just to play in foreign leagues. For this reason, many criticize these players, but if we consider their issues from the perspective of those players, then we will feel that what these players are doing is not wrong. The West Indies Cricket Board is not a developed enough cricket board, they cannot pay the players properly, many times such issues have come to the fore that West Indies players are coming to play the World Cup tournament on their own funds. Maybe no cricketer would want to ignore such a big offer of money and play for the national team for free, that is why they play cricket for the national team for a while and then when they get good recognition in foreign leagues, they retire from the national team and focus more on earning money.
The reason for retirement from the national team to play foreign leagues may be that the cricket board of that country has not been able to properly evaluate the players. If I talk about West Indies, then I have to say that most of the players from West Indies play foreign leagues more and so far there is no foreign league where West Indies players have not been seen on the field.
I think West Indies players retire very quickly to play foreign leagues because they do not get proper evaluation from the cricket board of the country.
As you said about South Africa, to be honest, I have not seen the players of the South African cricket team retire in that way.
Quinton de Kock, AB de Villiers, Faf du Plessis, JP Duminy might be good examples for you. Quinton de Kock retired from the South African national team despite being in great form only to give more priority to foreign leagues. Faf du Plessis retired a long time ago but when he decided to retire he was in great form, still I see Faf du Plessis playing in different T20 leagues especially IPL every season he is the auto choice of different teams. Again AB de Villiers' retirement was really unexpected and many thought that AB de Villiers might come out of retirement and return to the national team but that did not happen. Apart from the few names I have mentioned, I have seen many other cricketers who could have played more time for the national team but they retired from the national team only to give more priority to foreign leagues.