2x4s are strong, but they do have their limits. There's a reason that we don't just use two of them to support the weight of an entire car. There's also a reason that we don't try to slide cars off of trucks sideways at a 45 degree angle. The reasons are pretty damn obvious for all but the stupidest groups of people.
This is clearly one of the stupidest groups of people. You'd think that anybody with a 2nd grade education, or who had ever experienced gravity, or who has seen wood before, would have known how this would end, but this is apparently not the case. We can be reasonably sure that at least one of these men has experienced gravity before. I have personally been to Eastern Europe, and I can report that gravity is a thing over there as well.
The scariest part: at least one of these dudes is probably a licensed driver.