content: Another important point is the car is also a bit older. Watch this video about how a differential works. Open differentials in cars today work the same way where power follows the path of least resistance generally. What that amounts to is once a single drive wheel in a 2WD car begins to slip it effectively becomes a 1WD automobile and that wheel is the one with the least amount of traction. It's a mostly necessary design but it's absolutely horrible in snow and its what allows cars to get stuck in like 2 inches of snow. A 2WD car with traction control or electronic limited slip is still far far superior in snow to older 2WD cars but there is no easy way to market non-shitty 2WD cars so people just buy AWD's that do this will all wheels instead of just 2. The concept can be pretty simple and cheap to fix. When one wheel has no traction and is just free spinning the car grabs it with the brake pad to divert power to the other wheel that has traction but is doing nothing with it. It can be done fully electronically without any additional hardware for much cheaper than powering all 4 wheels. A modern 2WD BMW probably would not have done as poorly but that was an early 2000's model without it probably.