What is the usual process for organizing such an event? Is it calling for participation and then picking the best speakers for the deck (candidates -> organizer

What is the usual process for organizing such an event? Is it calling for participation and then picking the best speakers for the deck (candidates -> organizers) OR is it a sort of organizers choice of speakers who are then contacted (organizers -> candidates)? In either case, shouldn't organizers have the right to pick whatever they think is most interesting and then let their auditory choose, whether to participate or not in their event? By the very same logic, shouldn't editors have their right to choose what content they publish, with their readership voting for that choice using their wallets? I think in the end, if it is really important enough, underrepresented parts of community are still able organize their own conference, with all the right speakers.