Pure guess here (in line with the article!).
Judging by the frequent occurance of undercarriage collapses and damage in air accident reports, this aircraft may well have suffered hidden damage that caused a collapse at a later date, or expensive remedial work when it was discovered during a subsequent service.
The "no visible damage" remark is probably the crucial clue.
Just one of those things, but the lesson here is that if you have a heavy landing or a rough aborted takeoff, then it should be reported and the aircraft checked. Too many people get killed through embarrassment, or shame.