they discovered from scratch themselves If you followed the data compression scene in the 80s and early 90s, there were plenty of reinventions of LZ-ish and Hu

they discovered from scratch themselves If you followed the data compression scene in the 80s and early 90s, there were plenty of reinventions of LZ-ish and Huffman-ish algorithms (I also coded my own variant...), and people even tried to patent some of them, so at least for the basics I think it is something that many can discover independently; of course in these times, it's more likely they didn't.