。
He fleeced a gullible sucker out of a large sum of money.
Literal
He [topic-は] good-natured dupe [from-から] large-sum [obj-を] fleeced [polite-ました].
お人よし 'naive good person / pushover' literally 'honorable-person-good' — someone too trusting. カモ 'sucker / dupe' literally 'duck' (an easy target). 巻き上げる 'to fleece / swindle out of / reel in' is a compound verb (巻く 'wind' + 上げる 'raise'). The sentence stacks two synonymous victim-descriptors for emphasis.