When I was at boarding school a guy had a portable gramophone and a relative in South Africa who had sent a couple of "ethnic" records. They stayed with me as an earworm for years. Tin whistle very prominent. It still evokes that "discovery" of youth.

Paul Simon said he was captivated by a music tape I assume was similar, and with a lull in his career decided to follow his whim, as all creative people do.

He didn't bring down apartheid, but the album certainly drove at least one nail in its coffin. Simon is a very astute guy, he maintains he wasn't scoring political points with the move, but he is such a nice guy he must not want to upset his detractors who were vociferous at the time. Which increases his stature all the more. IMNSHO. And he ain't an average songwriter neither!
He, first and foremost, just wanted to make music. As Joseph Shabalala said "They used him, as much as he used them".