>>10949662>>10949661Just because it decays into those parts doesn't mean it's made of those parts. It's basically because you can tilt Feynman diagrams 90 deg on their side and obtain another, new, valid diagram.
Quantum fields are coupled to each other, so exciting one can excite others. Hence when a neutron decays, the quark fields undergo some dynamics, and this causes e.g. the electron and neutrino fields to vibrate as well.
