As with all design on aircraft, weight is a key part of the specification. A nacelle that could contain all possible failure modes would be too heavy to fly.

Losing a fan blade, as demonstrated in your two youtube links, is both a more likely event to occur and low enough energy to be able to contain with a reasonable structure.

However consider the situation in [0] where a turbine disk became detached from its shaft. The disk is still taking power from the exhaust gas, but rather using the energy to power the compressor or rotate the fan it is now just increasing its own kinetic energy. This continues until the incredibly strong turbine disk rotates itself apart. From the linked article:

> For engineering purposes, disk fragments are assumed to have infinite energy at the moment of release; they will cut through any reasonable material and cannot be contained

You can see from photographs of the aftermath, the nacelle is missing where this happened

[0] https://admiralcloudberg.medium.com/a-matter-of-millimeters-...