Why is it reasonable that beach tourists may venture there at night, but not reasonable that they would make the same trek earlier in the day?
I would contend that Medieval Times might even have more of an uphill battle with the location, since like you said, it’s essentially a glorified restaurant. I would think that it’s much harder for a restaurant to convince people to go out of their way to visit it, rather than a theme park which requires lots of planning anyway.
Maybe you're right, but considering the restaurant has multiple locations it's possible that many of their guests/customers already had positive associations with the brand and it's far easier for them to make an impulse visit for dinner while still having plenty of time for the beach during the day.
And, unless I'm mistaken, they usually do everything indoors which helps in the high heat/humidity of the coastal South... Or during inclement weather.