to make himself look successful after his failure in Iran. Choosing to attack a communist nation and long time political adversary of the US boosts his image. Americans are accustomed to thinking of Cuba as an enemy. It was dangerous in the Cold War as a Soviet Ally where the Soviets installed missiles.
The Soviet Union no longer exists and Cuba poses zero threat to the US. But the American people's impression of Cuba has not changed in the decades since the 1960s. So Trump is using that image to pose as the great hero who rescues the Cuban people from communism.
His real reasons are, as usual, far from the phony image that he projects. He is carving out the entire western hemisphere as his domain, under his control. In his mind, he owns not only the US, but all of North, South, and Central America, plus all of the Caribbean islands.
Trump's dream for Cuba would be to restore crime mob rule there, like it was under Batista. He would make it a playground for the wealthy, with casinos, brothels, and poverty for the general population. Those are the conditions that led to the overthrow of Batista. Castro initially promoted socialism. It was US constant efforts to overthrow him that pushed him into communism and defense aid from the Soviets.
I oppose communism as a dictatorship from the extreme left, just the same as I oppose fascist dictatorship from the extreme right. But Batista's RW dictatorship was so bad that the Cuban people's lives improved materially after he was overthrown.
If the US had not maintained hostilities and cut off all contact and trade with Cuba, we might have been able to influence Cuba toward democracy, but peacefully, not through miliary threats of invasion.
EDIT TO ADD: Mob elements in the US want their Cuban playground back. Trump's failure in Iran makes his goal of a Gaza resort unfeasible. Too dangerous in the Middle East where terrorism is more common than water.
So Trump is shifting his focus to Cuba.
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