Surely the dealers leasing those vehicles are factoring cost of maintenance into the lease, no?

See it as an insurance. It's not likely something will break, if you are the unlucky one though, those spare parts aren't cheap. A dealer can distribute that risk over many more cars.

I've never owned one but the folk wisdom I've always heard is to have a good foreign car indie mechanic (or do a lot of your your own work I guess) or just plan on keeping a BMW/Audi/etc. to the end of the warranty period because dealer bills add up fast afterwards.

Even if German cars don't last, when they roll off the assembly line, they don't have panel gaps and loose or missing parts.

There's also a difference in brand positioning. If I know nothing except the car one drives, driving a Tesla, BMW, Audi or Mercedes conjures up different stereotypes in my mind. Which manufacturer wpuld you associate with the following: a Senior VP at Goldman, a petrolhead who does occasional track days, a Bitcoin millionaire, a suburban mom, a FAANG L5 SWE in the SF Bay?

Your reasoning is based on 5 year old data. A lot has changed since then.