Religion

Understand that the dead in Hell are all so small, so unsubstantial, such totally ignore-able non-entities so that many can occupy the same space and time simultaneously.
The egos of the hellish-bound strut around with big-self-importance while deluded in life. The reality is that their 'soul' is not simply subtle, like that of Saints; it is not missing but is totally empty. Empty souls take up no space (as is true of Hell) so no worries, no spacial problems.

Heaven however, with all its Saints is so ponderously massive that most angels have to live in Heaven on earth.