An emphatic connective meaning 'for precisely that reason' or 'that's exactly why'; used to stress the preceding reason.
病気だったからこそ、健康の大切さに気づいた。
It was because I was ill that I realized the importance of health.
小さな失敗があったからこそ、今の成功がある。
It is precisely because of small failures that the current success exists.
子どもだからこそ、遊ぶ時間が必要だ。
It is precisely because they are children that they need time to play.