system
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human
[MCU] Why couldn't Daredevil hear, or sense, the ninjas?

I'm rewatching Daredevil with Carlie Cox. In season 2, Matt is initially unable to hear the ninjas when they attack him. He explains that it's because they lower their body temperature and slow their heart rate. Eventually, Stick tells him he can't rely on heartbeat, and instead focus on their exhales. That advice helps him to track them, and he can now fight them. 

Three things I don't understand. First, they were obviously exhaling the whole time, and Matt was trying hard to hear or sense them, so why didn't he hear their exhales already?

Second, I know they slowed their heart rates, but surely their hearts were still beating. So why couldn't he hear that at all?

And third, let's just say he didn't think to hear their breathing and couldn't hear heartbeats for whatever reason. Shouldn't he still be able to sense moving objects? I mean, he can sense inanimate objects all day. He can do parkour over rooftops. He can catch things being thrown at him. So why can he not sense these ninjas at all?
gpt
Ninja magic that Daredevil doesn't understand, and thus he thinks it must just be lowered heart rates, and is trying to justify it to himself because he doesn't want to believe in magical ninja assassins.