The Hellfire Club is only known by the Mutant Underground, other mutants and a few law enforcement agencies. People outside of it still have no idea how well connected and show skilled it is. The only people who really drew attention to it were the Von Struckers and since then it faded into obscurity. It's thrived and flourished in the shadows and forgotten by the majority of humanity. Anyone who tries to get more knowledge usually ends up vanishing or in a accident. 

But after the revolution everybody will know about it and it will be the most successful and infamous mutant group because it will win. It'll have all of us clapping when our banners for those of genetic difference are hung. It will freed from the restraints that's dragged it down for decades as it establishes a better world in the light.