The UK situation, for example:
>"Officially called a “Tier 1 investor” visa in the UK, the scheme gives individuals residency in exchange for investing £2m in UK bonds or shares through a bank, with applicants eligible for indefinite leave to remain, and even full citizenship, after five years. That is, unless they can stump up more cash: those offering £5m can settle after three years, and those with £10m after just two." (https://www.theguardian.com/uk-news/2017/jul/04/golden-visa-...)
Now it's the Grauniad so I don't expect it to be completely right but I expect it's close -- [THIS BIT IS WRONG, PROPERTY INVESTMENT IS EXCLUDED: so make a company to buy your small pied-a-terre in London for a few £Million and you get access to citizenship.]
Things have tightened up recently for Russians, not sure about others.
See also https://www.gov.uk/tier-1-investor.
I believe it's for everyone, you basically have to indicate where your money is coming from to a higher degree of detail. It's an anti-money-laundering measure, I think, more than anything. The situation had become shameful, with London being the black-economy capital of the world.
... well, I guess that means I’m a lucky person when it comes to passports. When I reverse search, the best second passport for a German is “Application Error”, and I sure have plenty of those as well :)