They were the primary people saving those in the buildings. Without firefighters, rescuers and police officers, the people saved that day might not have been alive. They also risked their lives and some died but sacrificed themselves and their families for the survivors. So in essence, the first responders were the only people able to save the survivors and help those in need because the buildings collapsed.
By the way, what class are you taking where you’re studying this? And are you homeschooled or public schooled? Sorry for such personal questions. I just was interested!