Although Bosch is a German brand, a lot of production is now outside of Germany. For instance, some white goods are now made in Poland, and for a good deal of years a lot of washing machines were made in Spain.
I admit I know very little of their current vacuum cleaner ranges, including where they are made. What I do know is that in their day some 20 and more years ago, they were built in Germany and were sold in the UK under both Bosch and Hotpoint brands, although going back even further to the start of the 1980's, they were sold here as Hotpoint, and quite a range there was too. Despite the fact that most, if not all, Hotpoint cleaners were supposedly available as Bosch and Siemens, I don't recall this being the case in the UK until about 1990, nor did I ever get asked for the bags by a customer using the Bosch / Siemens name, they only asked for Hotpoint.
Although the quality of the cleaners was generally good, I wouldn't say it was any greater than that of Electrolux cleaners, and indeed one or two parts of the design -particularly hoses- was disappointingly poor for a brand with such a reputation for high quality and a retail price to match. I always felt the same about AEG too. Point is, there was a target market for cleaners which were perceived to be top quality, and Bosch, AEG, and Miele were able to cater for it. Of the three brands Miele was the only one I felt was worth paying more for. I'd also suggest that as the price of a good deal of Miele models was highly competitive, they were probably the most popular of the three brands.