Continuity mistake: During the ants scene, Indy is about to grab a stick to the left of his hat. In the close-up the stick and the hat have swapped sides.
Continuity mistake: While Mutt's bike is sliding along the library floor, right before it comes to a stop it's pushing a chair on the right. A frame later the chair has magically made a 180ยบ turn and moved half a meter to the right.
Continuity mistake: When Col. Spalko begins cutting the leather covering the alien corpse in the casket, no straps are seen. In the close-up shot a strap is suddenly visible.
Continuity mistake: In the race between the soldiers and the youngsters in the roadsters, there is a shot of boots on the military vehicle's pedals and the next shot is of sneakers on the same pedals.
Answer: People felt it was ridiculous and cartoonish, even by Indiana Jones standards. Even if it was possible to survive a nuclear blast via the lead lining of a fridge (it's not), or that the fridge would simply be thrown away rather than be melted/torn apart like everything else in the vicinity (it wouldn't), the impact of being flung what appears to be a mile or so through the air, then violently crashing into and rolling over the ground, would certainly kill anything inside. The controversy arose because usually, in "classic" Indy films, the fantastical elements were exactly that: fantastic, magical, and/or supernatural. This was presented as taking place in our reality, with no "power of God" or magic spells, and for many, that was just too much disbelief to suspend.