Except for the few Republicans in the Freedom caucus, Reublicans do not believe that deficits are bad. Trump is a strong adherent of this view that deficits from spending on things like infrastructure or from spending on tax cuts will result in growth that will result in reducing the deficit in the future. Trump's budget is based on this philosophy of stimulating growth with deficits then using that growth in the future to reduce the deficit and pay down the national debt. This comes from business where you borrow heavily now to leverage your investment today for future growth that eventually pays off the debt.