Well you did have large houses wiped out in one swoop, House Black used to rule from the seat of Harrenhal and ruled The Iron Islands and The Trident and House Durranden, who ruled The Stormlands and what's now The Crownlands, were both destroyed during Aegons conquest (Although the Durrandens sigil and words lived on through the Baratheons). Large houses were eliminated and major shifts occurred just not very often. In the books of ASOIAF the houses end up falling upon one another as they do because all the strife and strain which has built up has devolved into what is effectively a war across the whole of Westeros, something which never truly happened in the run up to the books.
When the situation's right all the pieces fall into place and results in a truly devastating war which changes the face of the world.
EDIT: I didn't summon all this info off the top of my head btw, been reading A World of Ice and Fire recently
When the situation's right all the pieces fall into place and results in a truly devastating war which changes the face of the world.
EDIT: I didn't summon all this info off the top of my head btw, been reading A World of Ice and Fire recently
