To a large extent the tariffs were imposed just before China traditionally started importing from Brazil, so for several months they had little effect on actual supply (a few ships did get turned away, but for the US it was slow season). Brazil has ended their shipments, and China is turning to other countries which are selling at inflated prices and then buying from the US.

Don't paint the above as good for the US - things are bad for farmers, they are selling below what the cost would have been. I'm pointing out that the picture is (as always) complex.