Generally speaking, getting your rally car onto a trailer for long distance drives is one of the safest means of transportation for these vehicles, but we’re sure you’ve heard of Murphy’s Law.
We can’t know for sure what happened here, but it appears that something went wrong with the locking mechanism and the trailer detached from the car.
The driver probably reacted like any of us would, voicing out his opinion on the matter in a way which required a heavy use of bleep censoring, which after all is understandable.
At the end of the clip, we find out that the losses were minimal and that after 30 minutes they managed to drive on to the rally.
You could say that they were lucky that trailer impacted the guardrail at the angle that it did, and at a reasonably low speed, otherwise the damages could have been much worse.