[My opinion]
The MT planners may have put their faith in increased & 'improved' airport security around the world; and have also taken into account Hong Kong's distance from America and the Middle-Eastern troublezones [cynically speaking: would Tom Brokaw or Mr. Rather devote an entire news broadcast to 3,000 dead Hong Kong citizens?] ...Take that for what it's worth...

More likely, the builders/planners are counting on the shape [conical], and its redundant structural-support [should an upper-section of the MT's support-structure be smashed into by a jumbo jet] and redundant hi-tech fire-suppression systems and emergency exits.

But even they know you can't protect
against everything. A mini-nuke could kill 100,000 either in ONE big building
like MT, or in a half-a-dozen clustered 30-story tall apartment bldgs. 100,000 dead is 100,000 dead either way.

Jacob