You speak of things NOT just unique to Polynesian-Hawaiians, but most all peoples in Hawaii. The Japanese lost their language, and so did the Chinese and Portuguese brought here by the King's Board of Immigration.  There were so many different languages that it was decided that English would be used to teach the children in school.  No one ever "outlawed" the Polynesian-Hawaiian language. But English is spoken all over the world. English was promoted by the Kings from Kamehameha IV on. 
Excerpt of Kamehameha IV’s speech givin in English and Hawaiian at the opening of the Legislature, April 7, 1855:
“It is of the highest importance, in my opinion, that education in the English language should become more general, for it is my firm conviction that unless my subjects become educated in this tongue, their hope of intellectual progress, and of meeting the foreigners on terms of equality, is a vain one”.