Just apply some logic...

Not touching that stash of BTC would have only 4 feasible reasons:
-The owner lost his key.
-The owner died and took his key with him.
-It's locked behind a multi-sig and the owners had a fall out.
-The owner is not interested in money (extreme autism).

I listed them from most high to low likelihood. That is all there is to it. Price protection, "wanting bitcoin to succeed" and superhuman restraint have nothing to do with it.