Stallman’s attempt to rename Linux to incorporate the GNU name not happening was frustrating on his end it seems. Everytime someone calls their system a Linux based OS and not GNU/Linux based OS downplays the work he put in. However, Linus’s kernel was more elaborate than GNU Hurd, so it was incorporated. It’s said Stallman is a visionary, while Linus is a programist. While there’s never been any display of tension in a back and forth between them online, it’s always seemed to me they appreciate and also despise various aspects of each another.