I did a search on this when the assertion was made about this. I think the nuance answer to this is that they thought they were good people, so they would not be deported. It was more of an idea that those people who are causing trouble, and are not them, would be affected by Trump's policies.
What happens a lot is one person who is charismatic makes a loud assertion, and then people run with it like it is the unvarnished truth. While they may have thought the darker immigrants who came here would be the only ones who would receive this treatment, especially Cubans, I could not find any evidence that they actually thought Black Americans could be deported.
Instead, they did not vote for Kamala more because of their inherent racism towards anyone darker than them, more so than them thinking Black Americans would be deported. They voted against their own interests, because many of them live in a bubble of being the majority in their little area, i.e. Miami Cubans, and were living the American dream of being the racist towards those others who came here on boats. Well the jokes on them, they were really just tools to fight Communisim, and that whole communism scare has been long dead for a long time now.