For instance sedans aren't popular in Europe. In the luxury car segment, the stationwagon is far more popular. Designers from Europe, designing for Europe know this. So they could conceivably design a Model 3 Stationwagon.
This of course is not the only difference in taste between Europe and the US. In Europe range is far less important: people rarely drive more than 250 km in a day. Most rarely drive more than 100 km in a day. So an entry level low range (say 300 km) cheap Tesla could be a succes in Europe and not even be marketed in the US. Such a car would be interesting to people leasing a car via their employer. Leased cars are taxed to the driver, and a Model 3 is getting more and more expensive due to changing tax rules.
So in Europe cars are simply different. Smaller, lighter. Other form factors (though the SUV Is getting more and more popular over here too). It's a smart move from Tesla to get a design team in Europe.
(Did you know Ford has models on the market in Europe that never existed in the US? We've got no less than 3 regular cars and a couple of crossover/suvs positioned below the Fusion!)