Bushido originally was fighters of all different weight classes. It was for some of the up and coming fighters as well as fighters that weren't featured as much on regular Pride event. It was meant to be quicker and more action as the others have mentioned. Bushido events used to have themes such as Team Gracie vs Team Japan and Japan vs the World. Around Bushido 7 they switched it to showcase the smaller fighters, making it LW and WW(MW) only, except for the occasional freak show match(Minowa/Butterbean,Minowa/Giant Silva).