mc misread the time and thought he was late so he ran as fast as possible to school even though he had plenty of time. His friend makes fun of his frantic behavior as he entered
there's still 5 min before the bell rings, even if you run with all your might like that... that was a waste of effort wasn't it(?)
logically "... was a waste of effort" makes sense, but what is actually written is more like "that's good isn't it? How does なにも at the start fit in with this?