The official final report cited faulty booster rocket O-rings and the media dutifully reported it with no questions asked, which is a total joke. If you operate equipment outside of their design parameters, it isn't the fault of the equipment or the designer when it fails. The real cause of the Challenger accident was gross mismanagement. The NASA brass does not want that to be the cause of Columbia's loss, too. That's why they're trying to find a magic bullet to blame the accident on.
When NASA implies that meteor collisions and sprites are more likely causes than the big piece of insulation that was filmed hitting the wing that failed later, what does that tell you?
Whatever you say Captain Queeg.