What factor makes the hawaiian islands the perfect place for plant species to diversity

Either the isolation of the islands, the variety of ecosystems found on the islands, or the nutrient rich soils.  Idk...

The nutrient-rich soils.

Explanation:

The Hawaiian Islands surfaced between 400,000 and 5 million years ago. However, the entire undersea chain has been in existence for over 60 million years! Still, in geologic terms, the Hawaiian Islands are relative newcomers to Earth. These islands are isolated in the middle of the Pacific Ocean. They were created by volcanic activity from the "hot spot" in Earth’s crust. These underwater mountains eventually surfacecreating islands. The resulting volcanic soil is rich in nutrients. As Hawaii is located in a tropical region, the climate provides warm temperatures and an ample water supply. These resources provide all the requirements to support an abundance of plant life. An unoccupied landscape offers a wide variety of empty niches. This is the perfect recipe for plant diversification.

allowed for the prediction of the properties of missing elements.