Hawaii became a Democratic Party state due to a number of factors, including the rise of labor unions, the influx of new immigrants, and the political activism of native Hawaiians.
In the early 1900s, Hawaii was a plantation economy, and the vast majority of the workforce comprised immigrants from Asia. These immigrants were often exploited by their employers, and they began to organize labor unions in an effort to improve their working conditions. The labor unions were successful in winning some important concessions from their employers, and they also began to play a role in local politics.
In the 1920s, Hawaii began to experience a period of rapid growth, and the islands' population swelled with new immigrants from the mainland United States. These new immigrants brought with them their own political beliefs, and many of them were attracted to the Democratic Party. The Democratic Party was seen as the party of the working class, and it began to make inroads in Hawaii politics.
In the 1940s, native Hawaiians began to become more politically active. They were angered by the fact that they had been marginalized by the plantation economy, and they began to demand a greater say in the political process. The native Hawaiians were successful in winning some important concessions, and they also began to vote in large numbers for the Democratic Party.
By the 1950s, the Democratic Party had become the dominant political party in Hawaii. The party's platform was based on the principles of social justice and economic equality, and it appealed to a broad range of voters, including labor unions, immigrants, and native Hawaiians. The Democratic Party has remained the dominant political party in Hawaii ever since.