This is the 8621st most frequent Japanese word.
故に
"故に" means "therefore" or "consequently."
In this sentence, '故に' introduces the reason ('being hardworking') that led to the consequent event ('success').
彼は努力家故に成功しました。
He succeeded because he is hardworking.
Here, '故に' indicates the cause ('lack of time') of the effect ('not having time to eat').
時間がない故に、食事を取る暇もありませんでした。
Due to the lack of time, there wasn't even time to eat.
In this example, '故に' is used to specify the cause ('lack of preparation') for the resultant failure of the plan.