Fusing of bombs in WW 2 was prone to errors. There were deliberately many steps needed to arm a bomb. Then there were different ways to "tell" a bomb to actually detonate: delay, barometric, etc. A plane that crashed should never have its bombs go off, unless eventually a fire sets off the explosives.
There are many accounts from US 8th AF of bombers "exploding in mid air" but I don't remember reading of any other aircraft caught by those explosions. Unless they collided. Even in a collision, main risk is from fuel not bombs. Of course fuses sometimes got armed accidentally - even in modern times.
The flip side of fuses designed for safety is duds.
Perhaps someone is familiar with current "state of the art"?
Probably not state of the art any more, but when I was in the service, the dumb bombs still had barometric fuses. We had (at Moron AB, Spain, 1991) an IFE on a B-52 coming back from a mission over Iraq, damaged by SAM (missing half of one horizontal stabilizer), and one of its Mk117 bombs (750-lb) hung up on the port pylon.
A/C made a safe landing and taxied to the hammerhead, where we firefighters were setting up on an emergency egress. Now, "rescue side" in firefighting vernacular is the A/C's port side. Aside from the rescue truck itself, I was driving the fastest crash truck in the station, an early-model P-19, so being second on-scene, we set up behind Rescue-9 to covers their ops and set up for turrets as the bomber was slowing. As it came to a halt, with R-9's crew just outside their vehicle, the bomber nosed down and jerked a little as it stopped.
At that point, the hung ordnance let loose and fell off the pylon, oh, I don't know, maybe 9' to the flightline, where it did a bounce-and-roll. You had firedogs running everywhere getting out of its way. R-9 scooped up some crew, and we took a couple ourselves into jumpseats, and both us got the FOOD. I had Crash-5 up to 60mph in what I think was record time as we headed to the 2500' pullback this bomb called for. We passed, going the other way, the two ancient P-4 trucks coming down the taxiway, huffing and puffing their little engines out to back us up, they hadn't turned around yet.
EOD came out later to secure the bomb, and the next day destroyed it by putting it in a farmer's field and setting it off. Crater was 75' wide and probably 30' deep if my old ass remembers right. You could drop a house into it. Me and Ram on C-5 helped snuff the grass fires. That was our excitement for Desert Storm.
Anywho, long story short, even 30 years ago, the fusing was fairly reliable, even if we didn't trust it.