The damage also depends on the shell and the cupola itself.
If the APHE shell overpens, then only the commander dies, or even survives, if the shell itself, and the few shrapnels do not hit him.
Try shooting a Tiger H1 in the cupola with something like the soviet 100mm or 122mm guns. It just straight overpens
When it explodes, it not only sends shrapnel all under (and a bit to the side), but it also creates a shockwave inside a metal box with thick inner walls.
Even with ear protection, it would damage the crew’s ears, deafening them temporarely, or even permanently.
And this is just the best case.
A strong enough overpressure can also damage the body.
If it actually detonates, it will send pieces of the unfortunate (or rather, in this situation i’d call him the fortunate one for at least not suffering) commander’s body everywhere, while painting the whole tank with blood.
If the shockwave did not stun and/or deafen the crew, then the psychological shock of seeing small pieces of your commander everywhere certainly would.
Blood is also gonna make verything slippy.
And if it is not enough, there is still the shrapnel. Watch this video:
it is a so-so similar case.
Tank shells are usually bigger and more powerful than a hand grenade, and even in the video, shrapnel got through.
An average 57mm APHE will have less explosive inside, however, it would likely create larger shrapnels with more penetrative force, so they are more likely to go through the commander’s body, and still inficlt significant, if not lethal damage to the crew nearby.
Lastly, for WT, there is this mechanic, called overpressure.
Now, you can debate if it is a better mechanic, than hull breake (i’d vote that both of them are BS), but around 190g of TNT equivivalent will trigger an overpressure effect with APHE.
This means, that all crew in the same compartment will die, regardless if shrapnel did hit them or not.
A great example are the following tanks:
Fcm 2c (with the 75mm gun)
All those 3 has a 75mm gun, and 200g+ of TNT, and they will always 1shot enything, if their shells pen.
Yes, even an FCM 2c with it’s 12 crew memebers will be destroyed. Just shoot the cupola on the turret, and even the rear MG turret crew will die.
That mechanic is a gameplay choice.
A similar thing happens in this video (tho shrapnel still hits the driver. There is just no 2c in the test drive, but i did this once to it with the Ho-I) :