Quite simple-there were many plots, many Dominicans were asking for help from the US government, the US government couldn't decide what to do. The plot that actually killed Trujillo was hatched by Dominicans, and there were many plans about how to kill Trujillo. Plans formulated by Dominicans. The plotters asked primarly for weapons. The CIA coughed up a few rifles(from memory-4). The machine guns and hand grenades were never handed over to the assassins, JFK balked at the last minute.
I interviewed many people involved in Trujillo plots, including the Chana Diaz(who was in on it from the beginning) and the Spaniard who made the shotgun shells(filled with ball barrings) that were used to kill Trujillo. None of them mentioned the CIA or any agents helping them plan anything. The final event was a last minute thing, many of the members of the action team(hit team) were out of town. There was also a part of the plan I was told about that included a land rover loaded with bags of sugar that would slam into Trujillo's car if he managed to escape the ambush(that was new information for me).
Perhaps this is another plot that I haven't heard about, perhaps. General Imbert never mentioned the CIA when I interviewed him. The Reid Cabral's did try to get American Governmental help, and it never panned out. The CIA bailed on the assassins at the last minute.
General Espailliat, in his memoirs, does discuss CIA involvement. He calls two CIA agents "Mutt and Jeff", and he claims the CIA contact man was Doctor Robert Reid, which is rubbish because Robert Reid(who did not survive the aftermath of Trujillo's death) was not involved in ANY plots, he was a complete innocent. Espilliat lies a lot in his book, I don't know if he was lying about this or just misinformed.
The men who formed the plot that actually killed Trujillo died in a gunfight with the SIM a few days after Trujillo was killed.