The Bitcoin Cash folks didn't want to use a new cryptocurrency, they already had bitcoin and wanted to use it more like cash (i.e., low transaction fees). Basically, there was a large subset of Bitcoin users who did not agree with the development roadmap as set by the core Bitcoin developers. The core developers did not do enough to accommodate this subset of bitcoin users (there are technical reasons why they refused to do so, though their validity is debatable), so the codebase and blockchain were forked. It's a little confusing, but the most reasonable outcome since the community was at a political standstill for years and now both groups are free to do their own thing.