The first globalisation moved grain, cotton and migrants; the second moved components, services and instructions. What technological change explains the difference?

C. Cheap communication and containerisation cut coordination cost

Baldwin's 'second unbundling': once coordination became cheap, production stages could separate geographically and each go where it was cheapest. Tariffs fell too, but a tariff cut without cheap coordination would still leave the factory in one piece, the binding constraint was information.