Why Av node is slow and Purkinje is fast?

Why Av node is slow but Purkinje is fast?
because
AV node has more number of small cells while purkinje has less number of large cells so depolarization has to pass many membranes in AV node than Purkinje fibers
AV node has less gap junction while purkinje has high number of gap junction
AV node depolarization is by Ca2+ ions  but purkinje by Na+ ions which is fast
AV node cells have less diameter which has high resistance
AV node RMP is -60mV while purkinje is -90mV so cations move faster in purkinje fibers

Source: Najeeb lecture videos