Maybe this diagram will help...I watched the first video, thanks, but haven’t finished the second yet, but it seems you still need a potentially difference for a current, and I’m still trying to understand how current returns to the battery on the negative side of the load.
R1, R2 are the resistances of the wires between battery and bulb, small but real. So the PD of the battery is split across the 3 components R1, Lamp, R2. In many cases R1, R2 could be assumed to be zero as they have relatively little effect, but they exist. Each of R1, R2 converts electrical energy to heat (V * I = 0.05 * 5 = 0.25W) but its tiny compared to the ~60W of the lamp.