To be fair, Hurd recently made a decent splash. And strictly speaking, it's troubles weren't specifically GNU. Without all the legal quagmire around BSD we would all be on it. Linux would just be some niche hobby project just like Hurd. It was unfortunately a victim of timing. Both in that sense and the direction computing took in the future. Heavy IPC across multiple discrete CPU cores is a bad idea for performance. It works but it's slooooow