I’m not surprised that there was a gear arrangement that provided enough mechanical advantage to rule the day; you can get more or less arbitrary amounts of that limited only by your patience and keeping the friction low enough that your motor can still overcome it.
What was surprising, and impressive, was how long the parts of the lego that actually did the direct contact with the axle held up.
They eventually failed; but the only way this worked was by having a few little plastic nubs endure better than the axle did. I would have expected them to deform or shear off much earlier; and then the arrangement to rotate merrily without actually doing any further work on the axle.
In summary and conclusion, the little axle interface nubs are the heroes of this documentary.
