I'd say Cook spread venereal diseases and discovered the Hawaiians didn't like that. They welcomed him as a trader, and he fired cannons at them to show dominance. The same method was used by Commodore Perry to open up Japan.

The reality was, that the traders who opened areas up were going into areas that wanted to open up anyway. Those who decided not to trade ate the traders. Trying to show it was some European dominance does not show up in any record or remark from the people at the time. Heck, Japan closed its doors several times to traders, and the attempts to open it up found a sharp response. Tongans and Samoans had tried to open up Hawaii to the rest of the world and were told off.