Because he's being overtaken on the inside, the X4 driver can't make the banked carousel and runs wide. And as he didn't brake sufficiently before that, his Sports Activity Coupe starts to understeer badly. You can see the driver frantically trying to steer left, but it has no effect.
Once you've given the apex to a faster car, you should always brake, especially in a heavy SUV. The Nurburgring is classed as a closed German road, so what you see as overtaking on the inside of the track is classes as normal left-lane passing by the M3, but that's what screwed over the X4.
A split-second later, he smashes into the right track barrier, almost taking out a Peugeot and C63 Coupe. Moments later, Nurburgring traffic grinds to a halt. We'll remind you that crashing at the Nurburgring is expensive - damaged barriers, towing and such can cost more than €2,000.
Nowadays, most people get track insurance for the day, so at least that should cover fixing the BMW X4. By the way, the damage it sustained doesn't look too bad - some panels and trim. However, the steering rack is broken, as you can see it's not being controlled after the barrier smash. Because it's de-badged, we can't tell what model this is so that it could be anything from a 20d M Sport to the 35d.