Look at the top 3 tidal constituents (Mf, Mm, and 18.6 year) in the following chart (note its plotted on a log scale) and then compare to the table below it adapted from R.D.Ray.
All the modelled ENSO time-series peaks align based on the assignment of tidal gravitational forcings in the last column $$V_0/g$$
The ranking matched the falloff in strength $$ Mf > Mm > 18.6y > Mt > Msm > Msq $$
Everything below this in strength are essentially secondary factors
This doesn't happen by accident, it happens as a result of a solution to Laplace's Tidal Equations applied to an equatorial waveguide topology consisting of standing-wave modes. Alas, the consensus will point to ENSO as being a chaotically-driven behavior as that is a default rationale if they are not able to come up with an adequate physics-based model.