Two things to think about:

1) I heard the tapes add up to many hundreds of hours, including observation of the prisoners in their cells eating, sleeping and other necessary functions...

Is this true?

What are the logistics necessary to "scrub" such tapes? They are so highly classified that it would take a significant percentage of the government's appropriately cleared personnel ...and on top of that, a translator is required to confirm the translations that were made at the time.

2) Compartmentalization...

Having worked 30+ years in and around classified projects, I can be very, very sure that the number of people who knew of the existence of these tapes early in their life was very small. And it is also quite common for the higher-ups not to be informed of sources and methods, including access to raw intelligence such as the interrogation tapes. This is done precisely to protect the personnel and techniques from compromise by politicians and bureaucrats "without the need to know". ...THAT is precisely why the president is read a concensus "summary" intelligence document.

To the degree these are the facts, I think it is reasonable to assume the following:

At the time when these tapes were made, concern about torture and the international implications of using torture was known, but so minor compared to the priority of preventing a follow up to 9-11 as to easily have been overlooked within the very small group of people cleared to the methods used.

Then, when the tapes were no longer deemed needed for intelligence purposes, the sheer volume of the material meant that no one having the rank to render judgement had the time to sit through the tapes and figure out what risk they actually presented. The higher management probably came to view the whole issue as a "hot potato" that no one was willing to handle.... time pressure was an easy excuse.

The career CIA officer who was responsible for this operation recently retired. I strongly suspect he chose to destroy the tapes his own with relatively low-level legal approval in the belief he was effectively "taking a bullet for his country..." (at least in his mind) if his action were to become known.

...what? You never watched "24"? You never read ANY spy novel? You never read ANY history of the intelligence services during any of the World Wars? MOST people are NOT lawyers... actions speak louder than legal briefs to just about anyone in positions of authority outside of the courts. This is especially true in organizations where people risk their lives "for their country" (or for their neighbors, e.g. firemen, police and other emmergency responders.)

Now it is all political one-ups-man-ship.

The guy, just praised last August by the DEMOCRATIC chairmen of the intelligence committees, probably will be dragged through the mud and possibly imprisoned for doing exactly what the politicians themselves would have done under the circumstances.... if they had the courage somewhere in their bones to actually take on such a dangerous task.

Such is life in this world... torture the torturer with one hand while sanctimoniously decrying all torture with the other.