Question

What action led wealthy planters in hawaii to fear that their sales and profits would decrease?

Answer 1

This was caused by a new imposition of a U.S tariff on Hawaiian sugar.

Answer 2

During the 19th century the US government gave Hawaiian sugar planters very generous trade conditions that made them earn large profits especially after the American civil war. But in 1890, the US Congress imposed tariffs on imported sugar and Hawaii wasn't part of the US at that moment.