As a result of his method for early music education, Shinichi Suzuki h

altair to your query

We don't know much about Suzuki's past nor even his current status . The simple question is whether he is still performing or whether he has vanished into the background. If he is still one the best teachers, then he entails simple present tense as in C. However, if he was good in the past or good from the past does not matter to us, since he may be still be one today. But C removes the doubt forthrightly by saying he is still seen
Another muddled factor is the unnecessary split between seen and known. Whether an artist is seen or known makes little difference as long his performance is good,
After all, an artist has to be first known as good and then only he will be seen as a good when more people venture to visit his programs live.

C must be passable without much ado.