PaulP: "Geophysicists appear equally clueless about the origin of the Chandler wobble (and Relative Annual Precession), which is a simple applied torque"

Since the Earth's core is fluidic, these are complex torques, necessarily. Relative Annual Axial Precession is almost as simple as a wobbling top, given the right Galilean Frame of the annual orbit. 26000yr Axial Precession is similarly fairly simple, in its Frame. No one should be "clueless" about these.

Chandler Wobble (CW) was harder to work out, but [Gross 2000 Journal of Geophysical Research] is generally accepted as explaining sustained Excitation of CW:

Excitation is not the same as harmonic forcing. Excitation often occurs anharmonically (ie. violin bowing). [Ray 2013] convincingly showed ocean bottom-pressure oscillation as the major component of CW. It is amply documented in Literature that ocean bottom pressure is indeed tidally dominated, as such an obvious fact to not require much repeating:

Geophysics is not really "clueless" about any of its major questions. There is a modern abundance of clues to reason from. Again, we can confidently predict weak tidal harmonic forcings (>0) in CW multi-chaos (and might even be close to rough calculations), but inherent first order Helmholtz Resonance of many geophysical oscillators is often dominant.