。
His greed led to his downfall.
Literal
Desire [possessive-の] depth [subject-が] him [object-を] downfall-made.
欲の深さ ('depth of desire / greed') uses the ~さ nominalization on 深い ('deep') — 'deepness of greed.' 没落させる is the causative of 没落する ('to fall into ruin'), turning it into 'caused [him] to fall.' Literary/moralistic register.