BMW has changed their engine direction over the last 10 years. In the past, BMW only produced two turbocharged cars, the 2002 Turbo from the early 70s, and the 745 from the 80s. They have jumped on the turbo bandwagon with both feet after the success of the 135/335/535 engines. They will soon put a turbo-4 in the Z4 that puts out mid 200s HP ratings. They also have "M" versions of their SUVs are getting turbocharged V8s. And as a complete shock to me, the current V8 powered M3 will be the last & only V8 powered M3. The next M3 engine is going to be a turbocharged I-6.
I think fuel economy and ease of manufacture are the reasons they have gone from the high-tech V10 & V8 engines to turbocharged V8 & I6 engines. They've probably hit the efficiency wall for their NA engines too... Turbocharging/Supercharging gives you a huge boost in performance for the buck.
Heck, Toyota even had a turbocharged truck in the 80s (22R-TE engine)...at least for a few years.