I'll present this concept another way. Would your motivation to save your daughter or mother be greater than your motivation to save a complete stranger? For me, the answer is absolutely yes. (I am sorry if that makes anybody feel uncomfortable, but honesty is important for useful dialogue.)

Accordingly, it's possible to be more motivated to save some people and less motivated to save others. I believe that concept came into play here. After all, we are talking about an unprecedented CPR effort that is likely to cause instruction manuals to be rewritten. Note that the rescuers spent some time with the girl before the rescue. They weren't strangers.