I think that is the crux of the matter. We are discussing which rights the people gave to the government, not vice versa. We know the founders and constructors of the Constitution took great care to limit the power of the central government. That was specifically the purpose of the 10th Amendment, to protect the states and the people from a powerful central government. The previous nine were to protect the individual against the government.
In that context, in makes no sense that the states would bind themselves irreconcilably to that government. Plus some of the states had a pre-nup.
Several states expressed reservations about this or that, but all states signed on to the same agreement.