Its not that BMW’s are crap in snow, its just that becuase there are so many BM’s on the road compared to other rwd’s it makes them look worse.
The fact is that most people who buy a BMW probably dont even realise its rwd, or understand how a rwd drives differently to a fwd.
Any rwd are fine if you have momentum, if you stop you can be knackered, even on a flat road the camber can be enough to stop you going any where.
Recently I have seen some really well driven BMW’s going very side ways under control, however I have seen plenty of fwd’s going no where fast stopping rwd’s going anywhere.