He probably figured the Lakers were desperate enough to agree to everything. No one demand was all that big, but he was asking for a lot of stuff - control over personnel, a salary well above the going rate, reduced travel, and a handpicked successor. Plus if you go by what the analysts say, the triangle offense is a bad match for Nash and Howard.
Nash played for D'antoni. Kobe and Howard played for him on Team USA. So they are familiar with his style.