They are working quite hard, even though we the fans don't see that.
They are putting in a lot of effort without us fans realizing that they are doing so.
ご質問ありがとうございます。
① "They are working quite hard,"＝「彼らはかなり努力している」
"even though we the fans don't see that."＝「私たちファンはそれを見ないけど。」
② "They are putting in a lot of effort"＝「彼らはすごく努力している」
"without us fans realizing that they are doing so."＝「彼らがそうしていると、私達ファンが気が付かないうちに。」
ご参考に。
アメリカ合衆国 
