By repeatedly threatening and relinquishing the tariffs, he creates uncertainty in the international market and forces businesses to end trade “voluntarily” for fear of these sudden and unpredictable price spikes.

He can claim The Free Market is doing the work for him without taking any actual heat for enforcing a policy long term. He can also periodically extort business interests and rack in money on insider trading by imposing or lifting sanctions at the demand of big market players.