Someone recently put up a good article on the rise of RB Leipzig.
All I know is they took over a small I think ninth tier team close to the city and totally rebranded them.
The club is hated in Germany as they see it much like MK Dons here as a franchise,which it is obviously. I think in a recent game the game was held up for quite some time as opposing fans went on the pitch to demonstrate about how the club came about. To get round the law you can't name a club after a business they call themselves Rasen Ballsport Leipzig with the emphasis on RB,
They rose through the leagues very quickly and support in and around the city grew and now Red Bull are building a 80,000 seater stadium in the south of the city.
There is still Locomotive Leipzig who the older ones will remember in the city who are in the fourth tier I think, but Leipzig is a big city so can support two clubs.
I think most of the above is correct ish