Is the difference in skill level in SoloQ really that huge? 4 Challengers vs 5 Diamonds.

Just watched a video, many of you may have seen it, of 4 challengers beating 5 diamonds in a custom game. I would think that the skill level between diamond and challenger isn't that massive, especially not to win without a jungler entirely.

The Diamond Rengar got fed at first due to have 4 quadrants of the jungle all to himself but the challengers completely destroyed the diamonds in lane. You would think that a diamond player would at least know how to use a numbers advantage, no? Is the skill level difference really that big?