Overall, he was one of the people who brought South African musical styles to the world at large, doing lots of collaborations with all manner of artists and blending his homeland's music with styles from all over the world, so in a way he helped set the template for the kind of Hans Zimmer/Lebo M. work that The Lion King lives off of. More specifically, while he was never directly involved with the production of anything Lion King - which I really hoped he would've been for the remake - he did have some interesting musical tangential relationships:
- He wrote the hit song "Grazing in the Grass" in 1968 (https://www.youtube.com/watch?v=qxXZF60EPdM), which - aside from being recorded by famous R&B/soul groups and becoming a New Orleans brass band standard - was featured in the end credits of The Lion King 1 1/2 as covered by Raven Symoné: https://www.youtube.com/watch?v=NPQFhatkySI
- Then there was his cover of "One by One" from the Broadway show (https://www.youtube.com/watch?v=nN99Bg1OwAk) called "Ibala Lami" (https://www.youtube.com/watch?v=m4F6hH_2y7I), although I don't know if the "Ibala Lami" refrain was already a then-traditional South African chant before Lebo M. used it for "One by One" and both ended up covering it, or if Lebo M. actually wrote it and Hugh was inspired later on to do his own version. Either way, it's great.
- Of course we all know "The Lion Sleeps Tonight" mostly because of its use in the original movie, but Hugh Masekela was actually married to S.A. singer Miriam Makeba (albeit briefly; twas a long and complicated relationship they had), who helped popularize the more traditional version of the song - and was probably the first big artist to properly give Solomon Linda (the song's original composer) proper writing credit (https://www.youtube.com/watch?v=0fEHguhykD8) - before eventually doing his own version: https://www.youtube.com/watch?v=Nd8MezPSSyE
- This last one is probably the most tangential while also possibly being the most influential. At the height of South Africa's apartheid regime in the late 1980s, Hugh Masekela was involved in writing the music for a musical called Sarafina!, a show about the titular high school student and her classmates who get involved in the Soweto Riots, a mass student protest against government imposition of Afrikaans as the de facto language of instruction that turned deadly when police opened fire on them. The show had a short but impactful Broadway run and arguably laid the groundwork for the stage version of The Lion King insofar as having Broadway-esque South African musical numbers on an American stage. (Plus, The Lion King usage of the name "Sarafina" was probably an off-hand reference to Sarafina!)
There might be other tangential connections, but I can't think of any at the moment. At any rate, I think this should be enough to suffice making my case for us as Lion King fans to take note of Hugh Masekela's passing. He'll definitely be missed on my end: https://www.youtube.com/watch?v=lWGsgbd5LY0