Good question! Korean people don't like mentioning or repeating the main subject when the subject is an obvious thing that the listen can guess. So both the ways how you think can be possible E.g. the country, Korea, is getting popular so it is good to study korean 한국이란 나라가 유명해지고 있어요 그러니 한국어를 공부하는 것이 좋아요 I love korean culture so i like to study Korean 한국의 문화가 너무 좋아서 한국어를 공부하는 것이 좋아요. In conclusion if you want to make it clear then you should say the subject or say it in different ways