[Fitzcarraldo]

I'm speculating, but if this was a terrorist act
its concievable that one or more tiles could have
been impregnated with explosive material that would
be ignited by the heat of reentry. All the explosive
would have to do is dislodge the tile, just a few grams
would be needed.

[cgbg]

explosive tiles

That would be all it took. But this is an old vessel and as we learned from the O-Ring debacle NASA does have periodic lapses of judgement, particularly at the top and particularly when there is political pressure to "stop the engineering gloom and doom BS and get on with the mission".

A Microsoft "perfection is the enemy of the good" mentality can easily cause disasters like this.