The Wish description for The Terrible Tyrant reads as follows:

A Skull Tyrant, largest of the Marrow's loathsome bony predators, prowls the caves above the great path. Slay the beast and keep us all safe!

Sounds fine, right? But when we find and kill the Skull Tyrant, notice the following:

• The room in which the fight takes place is quite isolated from the rest of the Marrow. Its entrance is locked by a huge gate, and the only way in is through some narrow passageways. Moreover, unlike all other Grand Hunts, the Skull Tyrant cannot be tracked using Hornet’s spider senses, indicating that they have not been "prowling" outside for some time. Thus it appears that the Tyrant had already been locked in here on purpose; surely they are no threat to the pilgrims passing nearby.
• If we look at the Marrow map, we can see two clear routes leading past this room. The one below it is treacherous, passing close to the lava, and only has a couple of pilgrim corpses alongside many wild bugs. The path above, on the other hand, has better paved roads, is marked with cairns, passes buildings such as the prison, and has a bunch of haunted pilgrims walking it. So in all likelihood, the room in which we fight the Skull Tyrant is actually below the “Great Path”, not above it.

The logical conclusion: the Skull Tyrant we fight in the Marrow is NOT the one referred to in the Wish description. Hornet read the pleas of Bone Bottom’s denizens, immediately forgot the details, found a different Skull Tyrant, defeated them and returned to collect her reward, never realising her grave mistake.

We lulled those poor pilgrims into a false sense of security by dispatching a false threat. The next moment, the original Skull Tyrant shows up and destroys everything.

It is entirely our own fault that Bone Bottom was ravaged. That’s right: YOU killed Pilby.