If something happens to a vehicle, what happens to the creatures that crewed it?
Crewed creatures are considered wholly separate from the vehicle themselves. They are not "on" the vehicle, and they don't share its fate in any regard or have any ongoing relationship with it. Crewing the vehicle merely means the creature gets tapped and has no further implications.

When a Vehicle is exiled then returned to the battlefield later, only that Vehicle is exiled, and only that Vehicle is later returend. The creatures that crewed it are not affected in any way, and won't be exiled in the first place. Similarly if the vehicle is destroyed or dies, this doesn't mean anything for the crew.

(Your Conqueror's Galleon gets exiled only at the end of combat, by the way, meaning it will do combat damage. It also returns to the battlefield transformed immediately, not at the next untap step.)