Initially the CIA wasn’t exactly trying to kill Castro, but they definitely wanted him to lose power and credibility with the people of Cuba, so they decided that maybe all they would need to is a little bit of character assassination. They figured maybe if they brought the charismatic leader down a few pegs, the people of Cuba might just do the job for them.
One way that they thought might work to destroy Castro’s reputation was to get rid of the beard. Castro became known for his beard as he came to power and he was even known as “The Beard.” They hatched the plan to put a power in his shoes that would cause the hair in his beard to fall out. They had operatives at his hotel and in position to put power in Castro’s shoes but for some reason the operatives did not follow through with the plan.
The other idea that the CIA had to destroy Castro’s character was to pump a television studio full of LSD at a time when Castro was doing a live broadcast. The figured large amounts of LSD would cause the leader to say plenty of ridiculous things or even talk about some of the bad things he had done, and as a result the Cuban people would no longer follow him. The plan was scrapped because of the obvious issues involved.
Given the political climate of Cuba and the devotion of his followers, it is unlikely that either of these attempts at character assassination would have been enough to accomplish the ultimate goal of the CIA: a Cuba without Castro. The lack of success with character assassination and Castro’s turn toward communism were the tipping points for the U.S., and the CIA was then given the authorization to try and assassinate Castro.