How does AP propagate in large myelinated neuron?

[TytoAlba95]

I am reading https://www.ncbi.nlm.nih.gov/books/NBK21668/#_A6137_. It mentions that AP propagates along the length of the neuron due to the passive spread of depolarization, but it is only for small (thin, I presume?) myelinated neurons and large unmyelinated ones.
My question is how do APs propagate along large myelinated neurons?

 

[BillTre]

I think you mis-understood what they were saying.
the section you linked to is saying first understand how we are explaining passive spread of a potential change, which you seem to understand.
The next section (Voltage-Gated Cation Channels Generate Action Potentials) explains how voltage gated channels make action potentials spread actively, which answers your question.