They probably assumed this is like a theme park or something and not an actual city that people actually live in year round. Cities having nice, people friendly places away from cars? Who’s ever heard of that?
Fun fact from Germany! These giant Christmas markets actually double as parking lots outside of holiday seasons! Everything is temporarily built on top of a giant parking lot!
Furthermore these tend to be close to both major hubs (Think like a central train station!) and some other event areas that DO need the parking (like a football stadium!). That way, while the holiday markets (plural, several a year) are off, the space can also be used as parking space for sports events hosted in the adjacent stadium!
Just some amazing German efficiency for you. Oh also they frequently get used as skateparks.
It's called an event space and it can't be occupied all year. There's stuff going on pretty frequently but when it ain't, it's gonna have to be a skatepark + parking lot.
It ain't just Christmas. There's holiday markets for every season and even off holiday there is frequent flea markets. It's even where popular bands will hold their concerts. Without a dedicated space like that, it's impossible to set up these kind of markets and fairs. It's inevitable that some days it'll sit empty.
You try setting up a ferris wheel and rollercoaster in the cramped areas of the city. It won't work.
As a German, I have never been to a Christmas market held in an event park. I know Christmas markets as just occupying the town square or city centre instead of a dedicated area away from it.
Event parks are in my experience usually just used for fairs, food festivals and sometimes concerts.
Also to add (having just spent a good portion of the season going to various Christmas Markets all over Central Europe), a lot of times these central square event spaces are essentially the roofs over underground parking garages. LOTS of multi-level underground parking garages in all these cities.
Well, they've probably been markets for some hundreds of years before they dug a parking cave underneath. Old cities especially get increasingly cramped with time.