Breakdown of Comme tu as tout perdu, tu aurais dû protéger le capital.
tu
you (informal singular)
avoir
to have
devoir
to have to / must
perdre
to lose
Questions & Answers about Comme tu as tout perdu, tu aurais dû protéger le capital.
How does aurais dû express a reproach here?
Aurais dû is the past conditional of devoir (to have to / must). While the present conditional (tu devrais) means "you should", the past conditional translates to "you should have". We use it followed by an infinitive (here, protéger) to express a regret or to criticize someone for something they failed to do in the past.
Why is tout placed between as and perdu?
In compound tenses like the passé composé, short pronouns like tout (everything) and rien (nothing) are placed directly between the auxiliary verb (here, as) and the past participle (perdu).
I thought comme meant "like". Why does it mean "since" in this sentence?
When comme is placed at the very beginning of a sentence, it translates to "since" or "because" to introduce a reason. If you were giving the reason in the middle of the sentence instead, you would typically use parce que.