Mask was a bigger guy, because the ones in the suits were fake big guys. They are not big guys, the scientific literature is explicit on the matter, and because they pretended to be they had to be punished by the natural big guy laws of the universe.
The chick in the mask died because she pulled it off, answering the eternal question, while Mask is literally a mask in his very being, he can't pull it off, so he can't die.