You have a point about multiple opponents, but most fights are one on one. As you say, most of them end up on the ground anyway. In BJJ they train to take them there on purpose. If the other fighter wants to stay on their feet, they would need to be very well trained in how to do that.maybe, but most fights ive been in or witnessed did not involve any amount of grappling and typically involved alcohol lol. and per real wrld fighting i dont think id want to be grappling in a street fight; way to easy for a friend of theirs to get involved and grappling is a 1 on 1 thing IMO. im not a self defense expert by any means i just know in a street fight to avoid going to the ground even if thats where most fights end up
As to the multiple opponent problem, BJJ can very quickly disable the other person if that's what the fighter wants. In most fights you can simple get the other person to submit and quit fighting without doing major damage to them. However, if you have to deal with more than one opponent, those joint locks turn into joint breaks and they can be done almost immediately. Many of them without ever going to the ground.