Bfel: You are half correct, the Brotherhood do not share technology with the populace at large. They also do not 'cower in their bunkers waiting for everyone else to die' They are waiting for the rest of the wasteland to get its shit together, hence their cooperation treaty with the NCR that THE NCR VIOLATED. Directly stated in game, the brotherhood agreed to act as part of NCRs military and provide them with advanced technology on the requirement that all advanced tech be handed over to the BoS for study and archiving, after the assault on Navarro, the NCR violated the agreement by seizing most of the Enclave tech on site. The BoS response was typically military, you violate the agreement, we take back our toys. This conflict is cited as one of the largest reasons that the NCR is so painfully overextended, as they just finished fighting a civil war against the most heavily armed and elite forces in the known wasteland.
Everyone talking about the 'cartoonishly evil legion': Go play fallout 1 and 2, the Master is cartoonishly evil. The Enclave is cartoonishly evil. Fallout is set in a pulp-comics retro tech world, so of course the badguys are ridiculously over the top, that is how comics and serials depict the bad guy.