Well considering that when the RAF finally did sink her, she didn't really sink... (Beause the fjord was so shallow)
She couldn't move, but then she hadn't moved much for a while anyway...
And they had to have another go to make her capsize...
Also thinking about it most ships sunk by airpower suffered damage from torpedoes (Yamato and Musashi included). Torpedoes couldn't be used against the Tirpitz. Bombs really need to hit something vital (magazine, parked aircraft, etc) especially on heavily armoured ships, as they generally don't cause damage which lets water in.
Look at the Bismarck (very similar to the Tirpitz), she was pounded mercilessly by the RN battleships when they caught her. They effectively destroyed most of her superstructure, yet she was still afloat. She had to be finished off by torpedoes/scuttling (depending on whose account you believe).
If Tirpitz was anything near as resiliant as her sister to above waterline damage then the lack of torpedoes may have had a very significant effect.
Ignoring the apparent inability of the FAA to hit a stationary target of course...
Nick