I mean no offense but, he gave her an ultimatum: change the law or I jump off a building. First, when someone says something like that, people tend to not take them seriously because who in their right mind is gonna commit suicide off a building just because a law isn't revised? Carrie Lam stood by her decision and did not allow herself to be pressured into changing the law..
Mr. Leung MUST have known she wouldn't drop the law, which means that he WOULD have jumped, no matter what the decision was..