Why does the “house” of Usher fall?

By speaking of the house, Poe is being allegorical to the
head of a household, the leader of a group, and the foundation of a family or
organization. As the Usher family dissipates as a result of their congenial disease,
their living head of household, Rodderick, is also fading away mentally and
psychologically. Being that he is also dying apparently, the house, the residents, and
visitors alike seem to be decaying slowly into oblivion. Therefore, the House of Usher
(which is also a title given to other aristocratic and powerful families such as House
of Versace, House of Windsor, House of Hanover) is coming to an end, and so are the ones
who carry the name of the house of Usher with it.