I found this comparison video which show how essential lockers are on these heavy Land Cruiser wagons - not just for capability, but also protecting the IFS. The '99 LX470 (rear LSD only?), really struggles on the hill climb after the 80 and 200 get up with the help of momentum, good lines, and ATRAC in the case of the latter. The driver of the 100 series may have been inexperienced and had less traction after the trail being churned up by the preceding 80 and 200 series, but he does end up breaking his front diff - likely R&P and spider gears. 80s and 200s can break too in similar situations, but the CVs are usually the fuse instead of the diff, as I understand it.