When you travel to Japan and go to an Indian restaurant, the food tastes and is presented differently than it is in India. Then if you travel to Greece and find a small Indian restaurant, the Indian food is different there from the other versions. Same in Africa, South America, Europe. All of the Indian food sold in these places are nearly unrecognizable from each other.
This variation isn't limited to Indian food. It's the same with Thai food, Chinese food, Indonesian food, Italian food, Mexican food, Greek food, Japanese food. The ways of preparing and presenting these cuisines in foreign lands are as varied as the countries themselves.
It's probably a human universal: restaurant owners of ethnic restaurants change recipes to suit local taste and popularity.