projectiles
are complicated. At high speeds, strange things happen to colliding materials. Look into the properties of shaped projectiles for why you don't see the damage from the wings...it all gets sucked/pushed into the hole.
Myself, I'm surprised the towers lasted as long as they did after impact. Any building that size is a balance of forces - a system, if you will. Disturb it too much and it fails.
However, much remains unknown, in the shadows, under the black sharpie of redaction.