Here and elsewhere in this thread you are giving a misleading impression of the GOP's and Reagan's relationship to sanctions legislation. They fought it tooth and claw, and were eventually shamed into doing something, which turned out to be as little as possible, too late to matter.
That's what the parent comment is trying to get across. I have no idea why you're failing to see the distinction between legislators genuinely working on an issue vs. being dragged by public opinion.
The background is that most of the GOP leadership (political and think-tank) rejected sanctions against the apartheid government of SA during the 1980s. Similar to other muddles today, a cloud of confusion was thrown up to stop or delay passage of US sanctions. ("Sanctions would hurt the poorest most", etc.) It was all just a BS rationale to keep from implementing sanctions against a government considered a US ally (the ANC was associated with Communism), but it was all taken seriously at the time. Vintage Cold War logic.
A watered-down bill eventually passed the Democratic House, and went to the GOP-controlled Senate, where it was diluted and barely passed. Reagan had not anticipated this, and vetoed the bill. And it was then over-ridden. His administration never went along with the sanctions implementation.
By the time the GHW Bush administration took over and did somewhat better, the jig was up. The Berlin wall fell in 1989, removing the "bulwark against communism" rationale for US support of apartheid, and Mandela was released from jail in 1990.
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I have some attachment to the issue because my roommates were involved in sit-ins, a tent city, and other political organizing at the time. It was a defining issue of the mid-1980s.