Or buy them from Brazil. Like they are now since the tariffs happened.
It's not a question of switching to Brazil. China was already buying from Brazil. But Brazil doesn't have the capacity to make up for a cut-off of American supplies.
Further, soybeans are seasonal. The reason that China buys from both the U.S. and Brazil is because they have harvests at opposite times of the year. Even if Brazil managed to magically ramp up to fill 100% of China's need in each Brazilian growing season, what is it going to do the other six months of the year?