The bombardment early in the morning of 18 July was the worst we had ever experienced in the war. Although we were in foxholes under our tanks, we had a lot of casualties. Some of the 62-ton machines lay upside down in bomb craters 30 feet across; they had been spun through the air like playing cards. Two of my men committed suicide; they weren't up to the psychological effect. Of my 14 Tigers not one was operational. All had been covered in dust and earth, the guns disadjusted, the cooling systems of the engines out of action. Yet by early afternoon a few of my Tigers were ready for battle. I was to use them to attack westward in the flank of the British tank attack.
-excerpt from Panzer Commander, the Memoirs of Colonel Hans Von Luck.
Tigers are most certainly not invulnerable, even to near-misses by bombs. It doesn't take a lot of explosive to render a tank inoperative, just enough in the right place. M1A2's in Iraq have been flipped over by IED's which were nothing more than 2-3 155MM Howitzer shells wired together, that's not even 500 lbs of explosives. And the Abrams is 10 tons heavier than a Tiger.
The deadliest (to human) part of an explosion is the shockwave, which can cause severe stress on the body, rupture ear-drums, shatter bones, disrupt organs etc. etc. etc. Being inside the tank goes a long way to protecting the body from the shockwave, though. Because the shockwave is omni-directional it dissipates very quickly and something as small as a table-leg can prevent lethal effects by disrupting it's path somewhat. (The Hitler Bomb) Even being a few feet further from the blast than someone else can greatly reduce the effect of the shockwave as it operates much like the intensity of sound, because it is after all just air being pushed outwards.
So, in answer to the thread. Yes it is wholly feasible that the smallest bomb we can drop in AH2
can kill a tiger, it is also highly unlikey, but thanks to the laws of probability it is possible, and therefore will happen. Even if it's one drop in 50,000. It will happen. And... hey... it happened.
You were just unlucky enough to be there when someone had a good day.