For one, Cadillac has all but disappeared as a popular luxury car maker in the US compared to the Euro brands. It used to be that the Cadillac was the go to brand for Americans wanting to show off their $. Mercedes Benz was a distance second. Audi and BMW were more for Road and Track magazine types and had a pretty small market share. And the Euro auto makers were not very serious about making US vehicles because they did not like having to deal with US emissions standards and catalytic converters. So, Euro brands were not very reliable because they were not really making vehicles for the US market with the same care as the Euro market.
After Cadillac's decline, the Euro auto makers realized that they could really make money in the US and finally started embracing designs that worked well with required US emissions equipment. Reliability went way up. Entry level models (BMW 3 series, MB C series, etc) expanded popularity. SUVs expanded on the popularity. Now, Euro models are the go to brand for luxury vehicles in the US.
Thanks to very low interest rates, most smart people who have a lot of money will lease luxury vehicles instead of owning. This has translated into a very steady stream of very well cared for used vehicles landing on the market. Those vehicles are able to last much longer than they did in the 70s and 80s. Many are still marketable after 6-8 years on the road and close to 100k miles. So, anyone who has a middle class income can buy a Euro luxury vehicle for the price of a new well equipped Camry or Honda Accord. Younger singles think that driving a Euro luxury vehicle is a prerequisite to dating success. People in sales or any field where you have a lot of customer/client contact want to look like they are doing well to inspire confidence in their customer/clients. And then a lot of people come from families where their parents had a lot of money and always drove Euro cars. That can also be a big factor.
Of course, it is not money well spent. As good as the Euro cars are, they are still subject to the laws of thermodynamics and can suffer major failures at any moment once they hit 100k+ miles and generally are very buggy due to the nature of high performance engines, meaning lots of trips for service. For the same price, most everyone can afford a new Japanese car and not have a single repair bill for five years.