One possibility is that Maduro’s security detail, mostly Cuban counterintelligence, have access to damaging Epstein records. Epstein was in contact with Castro as of 2003 and was able to travel there despite sanction which would have prevented less-connected people.

FWIW, traveling to Cuba from the US (via flight from Canada, Mexico, or a dozen other convenient spots) has never been difficult, even for completely non-connected citizens.