I was thinking about this and discovered a pretty simple answer.



The original Japanese version is called Rhythm Tengoku. The latter part of which translates to either heaven or paradise . The thing is heaven doesn't look similar to the translation of the word in English. For example in German it's himmel and in French it's paradis which brings me to how the word for paradise looks more similar to the translation of the word in English. In German it's paradies and in other languages it's similar too. So if it was Rhythm Heaven in Europe some people might not have known what the title meant.



So in summary it's because paradise is more similar to paradies than himmel is to heaven .

Thoughts?