ご質問ありがとうございます。
「きっかけ」はtriggerと言いますが、triggerを文法的に使うのが結構難しいです。
例:My friend who likes saunas was the trigger that made me like saunas.
例:I happened to see a game of the Japanese team in the Olympics and that triggered my interest in basketball.
ですので、上記の回答ではより簡単な英文を提案しています。
例:I started to like saunas because of my friend who likes them.
例:I started to like basketball thanks to seeing the Japanese team play in the Olympics.
ご参考いただければ幸いです。