That is based on population. China is second but its people aren't rich as a whole. They have some rich people and a growing middle class.
Austerity meant public services were underfunded. This meant the bottom 20% were affected but the middle classes were largely unscathed. They simply dodged it by moving their children to private schools or state schools in leafy suburbs, got private health insurance for elective procedures. They coped. The cost of living crisis means that it is harder to use disposable income to cover the defects of the state. and this is why the middle class is suffering. Particularly as the middle class is accustomed to consumerism, inflation hits those who consume the most, along with the poor.
We are quite far down the list based on gdp per capita (which is total GDP divided by the number of people).
data.worldbank.org/indicator/NY.GDP.PCAP.PP.CD?most_recent_value_desc=true
Most Recent Year Most Recent Value
Luxembourg 2021 134,753.8
Singapore 2021 116,486.5
Ireland 2021 106,455.8
Qatar 2021 93,521.4
Bermuda 2021 85,192.3
Norway 2021 79,201.2
Switzerland 2021 77,324.1
Macao SAR, China 2021 73,802.2
Cayman Islands 2020 72,481.0
United States 2021 69,287.5
United Arab Emirates 2020 66,766.1
Brunei Darussalam 2021 66,619.9
Hong Kong SAR, China 2021 65,972.6
Denmark 2021 64,651.2
Netherlands 2021 63,766.9
San Marino 2020 59,571.9
Sweden 2021 59,324.0
Belgium 2021 58,930.9
Austria 2021 58,427.5
Germany 2021 57,927.6
Iceland 2021 57,646.4
Australia 2021 55,807.4
Finland 2021 55,006.6
Canada 2021 52,085.0
France 2021 50,728.7
United Kingdom 2021 49,675.3
Saudi Arabia 2021 49,551.3