What happened to the Blackhawks was dreadful, but I say DC's dumbest Silver Age decision was to move Legion of Super-Heroes from a full-length feature in Adventure Comics to a back-up in Action Comics. The Blackhawks were going to be cancelled anyway, but Legion was still popular in Adventure Comics when it was moved to Action, and with its epic scope and large cast it needed book-length stories. I realize the reason was to give Supergirl, who had been Action's back-up feature, her own book, making her the star of Adventure, and that she deserved her own book, but why did the Legion have to suffer?