Question

why did Nicola and jacopo destination in poleta surprise the narrator

Answer 1

On reaching Poleta narrator was surprised to see the large red-roofed villa as the narrator imagined their destination would be some humble dwellings

Answer 2

They were poor but still went into a big Villa like hospital.The narrator was surprised to see that these poor looking boys were rich at a point of time and are earning just for the operation of their sister.