Your points about electrical infrastructure are definitely thought-provoking ones. I'd agree that the infrastructure as of today doesn't exist for widespread adoption. At the same time, the market that Tesla and the luxury European automakers compete for today doesn't hit that 5% threshold (http://www.wsj.com/mdc/public/page/2_3022-autosales.html#aut...). Add up the market share of car (not truck) sales from BMW, Mercedes, Audi, Porsche, and you're looking at a ~3% market share.
I think this section of the video from Sandy Munro is worth a watch: https://youtu.be/CpCrkO1x-Qo?t=1730. Munro has been a huge critic of the build quality of the Model 3, but that everything "below the skateboard [the floor]" is seriously impressive. The cells in Tesla's battery pack have a maximum of a 0.2 milliamp difference between cells.
Say that I accept your premise that the German automakers today are biding their time, and could spend their R&D money on electric cars if they so chose. Who will they source their battery packs from? Will they try to build their own supply chain for the raw materials? What competence have they demonstrated in creating electric powertrains that deliver the acceleration and speed that we expect from luxury cars?
Lastly, I think your "market size estimation" here is dramatically off. BMW last year delivered 2.4 million total cars. They sold 103k "electric" vehicles last year, with 31k of the i3, and the rest probably being comprised of hybrid versions of their existing 3 and 5 series sedans. (https://www.press.bmwgroup.com/latin-america-caribbean/artic...) This was 65.6% year over year growth. For 2018, they expect "high two-digit growth" to continue. The demand is there, even from their own existing customers.
Among the reasons why, I would say there are many — engineering culture (and part of that is quality control and standards), haphazard management, brain leak (because of the competition poaching employees, unclear financials, and the management), financials (not making a profit and burning through money like crazy), dismissive approach to the competition and other company's engineering efforts and solutions (stupid robots everywhere, autopilot with the freaking webcams, when everyone said it's a bad idea).
I think the reason why we see that BMW, Mercedes, Audi and others are not building the electric cars with the same favorable characteristics as Tesla, and without similar fanfare, is because they have a bottom line that they'd like to stay in the black.
They have to know that electric car market is a very small niche right now, and they are letting Tesla to be the one who makes customers intrigued and creates some pressure for bringing up at least a little bit of infrastructure for the charging.
Imagine the daily commute in the big city, how many cars are driving through the main city artery? How many cars are pumping gas in any given 30 minutes? How many supercharger stations are needed to accommodate for this? I think you can create a societal collapse right now if 5% of the drives in US would switch to electric cars. People wouldn't find a place to charge their car, electric grid would become unstable and overloaded from all these people who hooked up Tesla to their 200 amp residential fuse box, while having dishwasher, washing maching, drier, TVs, computers and a ton of lights running. For fun, you can also imagine superchargers with enormous lines, with people reserving spots and selling them to those who are in a rush.
I'm sure that the blunt of BMW's and alikes engineering resources are spent right now in different areas, because they just can't afford building this perfect electric car which only 1% of their customers would want to buy. That's how you get bankrupt. Remember Apple Newton?