Now that is a great question. It’s fun to watch, but trial and error is not some form of higher intelligence. Why did the group persist though?
Discussion
Without an objective, it would be just like Brownian motion.
The object probably has a food-related odor and they are trying to bring it outside to the burrow.
Don't know about that, if not edited that video appears to show more than trial and error (which would involve more senseless repetition).
Just a personal opinion but to me intelligence would be based on the fact that they learned their strategy during previous attempts and/or they carry this strategy forward to future attempts.
In isolation we know nothing else about why they succeeded other than trial and error. If they were not successful we would be more inclined to ignore it and move on.