This is an oversimplification from someone who has only heard it from his Puerto Rican wife.

She said that there’s a large population of Puerto Ricans that distrust both the US government itself and PR’s. Some of that stems from deep seated anger and pain from the tourism industry, foreign investors buying properties, and a lack of support and representation from the US itself. The corruption within PR’s own government and how they’ll do anything they can for ‘support’ from the US, at the expense of their own identity and culture, while further burying themselves in debt to the US, led to the protest abstain vote movement among a significant portion of what would have been ‘no’ voters.

There’s probably someone out there who’s written a research paper/news article or two about it, but the biggest take away is that the majority of Puerto Ricans are not in support of Statehood. There’re large populations seeking independence, the status quo staying the same, and Statehood, all separately without a clear majority in any direction.