I ran into the Sinbad issue a few years ago and tried to back trace why I was remembering it incorrectly. This is what I pieced together:
Aladin and Sinbad (sailor) are both characters in The Book of 1001 Arabian Nights. The stories of Aladin and Sinbad were both popularized in movies/tv when I was little. (Note, I knew of sinbad the sailor before sinbad the actor). Aladin left a greater impression on me than Sinbad the sailor, and since I knew the were connected through 1001 nights, I would usually think of Aladin whenever I heard Sinbad.
My thought is that when I think of a "genie", I automatically think of Aladin. However, I'm only familiar with the cartoon portrayal, so when I try and visualize the human genie, the wires get crossed in my head and I simultaneously think aladin/1001 nights/sinbad, and Sinbad's face registers instead of Shaq's.
The above is a more complicated illustration of what someone earlier mentioned regarding the Ace Ventura/monopoly man monocle. An impression was made and it stuck.
Based on the examples listed in the OP, I'd wager that each of these mixups can be traced to an impressionable event from our younger/childhood years. Like Mandela dying in prison....I never get mixed up about that (because I don't recall knowing of him while in prison), but I bet the people that do can trace back to an event when they were a kid where that impression was made.
ETA: With Mandela, my theory is that the use of the adjective martyr when he was in prison is what makes people 'remember' that he died while incarcerated. Again, for a kid, the word martyr likely had connotations of death since religious (religious martyrs, etc)