@mogima aside from the humanities aspect, there is also good timing and atmosphere. Gill gave the speech when they were on the verge of giving the votes where at that point, everyone already laid out their negotiation ammo. Gill's speech is a new and unexpected ammo that came in when all countries have ran out of ammo.
There's also good atmosphere where every representatives gave standing applause to the speech. I can't tell if gill's speech is good or not but the author surely want to make us think that his speech is so good by showing the standing applause. Atmosphere can give a strong influence to where the negotiation is going. When the majority of people's feeling in one room is united, then the negotiation process will come smoothly and vice versa.
negotiation is a very dynamic process and so many factors can change the results. The process that went outside of the negotiation room is as important as the actual negotiation/voting part. And each of the process require different tactics too