Who knows if people even had the option to leave. Dictatorships usually restrict both information and movement rather severely.

From the reports I've read, it seems the storm surge was fast and severe (3.5 metres = 11.5 feet). Something about the strength of the storm and the shallow ocean topography made it especially bad. No warning of a surge was broadcast.

Anyway, I would guess that if you're dirt poor (barely enough money to eat), don't have fast transportation, and don't know a safe place to go, what are you going to do? You're going to stay put and take your chances. Harsh, but that's how it is.