Why Sam Mendes remained on his CV?
Eddie Redmayne means that his small role in Sam Mendes' production "Oliver" was listed on his CV for a long time, likely because of how respected Sam Mendes is in the musical industry. That is what he means by Sam Mendes remaining on his CV. You can also replace "remain" with "list" for more versatile verb usage. Ex: I was unemployed for a while, so even small part-time jobs remained on my CV. Ex: Students don't have a lot of work experience, so they often list volunteer experience on their resumes.