Pretty dusty
Back in the day before there was electricity, homeowners had to find creative ways to stay cool in the summer heat. In this dining room, the OP noticed a strange fan installed right above the table and presumed that it was used to cool the diners down during dinnertime. Their guess was actually spot-on.
Someone would pull on a rope, which was connected to a pulley system and cause this flat panel to move up and down. It would provide a bit of air to the diners below while also sprinkling their food in mountains and mountains of dust.