“Atom has not had significant feature development for the past several years, though we’ve conducted maintenance and security updates during this period to ensure we’re being good stewards of the project and product.”
Microsoft bought GitHub in 2018 and owned two code editors. One of them had to go, and it was never going to be VS Code. GitHub blames declining community involvement, after years of putting no features into the thing. Atom gave the world Electron, which Microsoft used to build the editor that replaced it.