meaning of "behind barriers of etiquette"

[Ofriendragon]

Hello everyone,
I’d appreciate it very much if you could help me with this paragraph.

In sixteenth-century Italy and eighteenth-century France, waning prosperity and increasing social unrest led the ruling families to try to preserve their superiority by withdrawing from the lower and middle classes behind barriers of etiquette. In a prosperous community, on the other hand, polite society soon absorbs the newly rich, and in England there has never been any shortage of books on etiquette for teaching them the manners appropriate to their new way of life.
Q：
1. Is behind barriers of etiquette an attributive of classes or an adverbial of withdrawing?
2. Can it simply be rewritten as by going farther away from the lower and middle classes who are already behind barriers of etiquette?
3．What does the underlined part mean?

Many many thanks in advance.

[Inga]

Hi!
What if the ruling families prevented/stopped the lower and middle classes from learning the manners?
At any rate, I'll be waiting for other members' answers together with you.
_________________
I am an incurable optimist.

[Jamie (K)]

3. The underlined portion means that the ruling families found that they weren't as rich as they used to be, and so they used etiquette to show the difference between themselves and the lower social classes. This was because at that time in history many people of lower classes were becoming richer than the aristocracy. Keep in mind that the economy and society of the time were changing, so that wealth became possible for someone of any social class who was good at business, and not just for the aristocratic classes.

1. "Behind the barriers of etiquette" describes the symbolic "place" to which the upper classes withdrew, not the classes themselves. A middle- or lower-class person couldn't enter the upper classes no matter how much money he had, because he had the wrong manners and speech.

2. It can be rewritten as meaning that, with less and less prosperity, the aristocrats took refuge in etiquette to distinguish themselves from the middle and lower classes, since wealth was not a mark "high birth" anymore.