Final answer:
The correct idiom should be 'struck oil', meaning to become very wealthy suddenly; thus the sentence should read 'The Suzukis are wealthy now, but we knew them before they struck oil'.
Step-by-step explanation:
The sentence you provided contains an idiomatic error. The correct idiom is 'struck oil,' which refers to someone who has become very wealthy, often very suddenly. Thus, the correct version of the sentence should be: 'The Suzukis are wealthy now, but we knew them before they struck oil'.