In fact there was a lot of churn and drama. What we have left today in the UK is literally the result of survivor bias.
A lot of country houses are now state-owned, managed through nominal charities. Quite a few disappeared in the 20th century.
The British aristocracy is a complex thing, with came-over-with-the-Normans at one extreme, and relatively recent self-made opportunists at the other. It's a socio-archaeological phenomenon in its own right - influential, but under-researched, and opaque to outsiders.
Heck, a whole TV show about it :-)
What little direct insight into it I have in the northeast US, it gets very complicated especially as large extended families get involved. People have very different goals with largely differing amounts of money and taste for spending it. Best is to run away in my experience.