Reading the comments found a lot of people saying "read it in a book by Junot Diaz" or "Julia Alvarez". Both are novelist and yes, they are very knowledgeable on Dominican History but their work is after all fiction. I have not read Junot Diaz; I have read Julia Alvarez "In the Time of the Butterflies" and they work have merit, but you'll be better served reading a history book instead of a work of fiction.
Frank Moya Pons book on Dominican history is a good starting point for those that are interested in this topic. Now, I have read about Trujillo supposedly wanting to get the country more white as the motivation for him accepting Jewish refugees and God only knows if that's true or not but I find that explanation suspect.
If that's really all he wanted, why only accept 700+ refugees? There were literally millions of Jewish refugees looking to escape to any country that would take them and the Dominican Republic when Trujillo came to power in 1930 barely had about 1,000,000 people. So if he really wanted to make the country more white just grant visas to 2,000,000 Jewish refugees and presto! Israel in the Caribbean! Tropical Zion.
Also, the other theory is that he wanted to atone in front of the international community for having order the massacre of thousands of Haitians, to which I say: Does Trujillo sounds like someone who gave a f*ck about what anybody would say about him? I think that a more plausible explanation is that when he offered to take over 100,000 Jewish refugees he was told that wealthy Jewish Americans will provide the funds to help settle the refugees and that when the money did not materialize he lost interest too...which sounds more like Trujillo is you ask me. Again, only God knows what he was really was after...don't believe me, do your own research into his character and see if you can come up with a better explanation.