There are a number of biological phenomena for which a plausible explanation in standard Darwinian terms is difficult to imagine. Metamorphosis is one, but others include the origin of life, the development of eukaryotic life, the origin of the DNA code, the evolution of irreducibly complex molecular machines and systems, sexual reproduction, the origin of multicellular life, the sudden appearance of the various body plans of living things in the cambrian era, and, perhaps most enigmatic, the emergence of human consciousness.
Why such phenomena would have ever evolved in the first place and how they could have done so are questions for which naturalistic Darwinism, or Neo-Darwinism, has no convincing answer.
There's a bit of overlap in the two videos but not much:
Speaking for myself, the idea that such a process, as well as the others mentioned above, evolved seems possible, maybe even plausible, but the idea that the process evolved unaided by any intelligent, purposeful guidance seems to me quite literally incredible.