The essence of negotiation was compromise. Both sides would need to give up certain things in order to come to an accord.
That's why, if you accidentally revealed what you wanted the most in a negotiation, you would completely lose initiative. If the other party caught on to what you wanted the most, then it would only be natural for you to lose the negotiation.
Thus, when I learned what Sandro wanted the most, it was destined that I would have the upper hand in our negotiation. Since our positions were unequal, it wouldn't be possible for me to lose in negotiation.
He needed my help. Meanwhile, I would be fine both with or without him. This unequal negotiating position allowed me to take the initiative as well as demand whatever I wanted.