I have read that Hawaii was found by Spanish but not colonized or explored. Why were other islands, for example the Philippines, taken over but Hawaii was left pretty much untouched?
In short, proximity to China was the reason.
The whole point of the Spanish being out on the seas, conquering the Americas and sailing the Pacific, was to establish a trade relationship with China.
They founded Manila, a place where the Chinese regularly sailed to for trading with Filipinos. They then proceeded to sell all the silver they could mine out of South America (Potosi - where roughly 80% of the world's silver came from) for fine Chinese goods ( China was the best and most sophisticated manufacturer on the planet at the time).
Source: 1493: Discovering the World that Columbus Created by Charles C. Mann.