Fuel consumption is a measure of power (eg energy per second) where as drag is just a force.
Fuel flow is a measure of the power going into the engines, but it is not a direct measure of the power coming out of them.
Power output / power input = Efficiency.
Unfortunately engine efficiency does not remain constant at all airspeeds, engine speeds and altitudes.
To calculate a "power" from a "force" you have to multiply by velocity
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That is true, but because of the variations in engine efficiency it isn't actually very useful in this discussion.
So in short fuel consumption is proportional to drag x velocity not just drag alone. It's the product that has to be minimised.
Drag x TAS = Power required. The value of this is minimum at Vmp. So the above quote suggests that best endurance speed for all types of aircraft is at Vmp. This is true(ish) for propeller aircraft, but not at all true for jets.
For minimum fuel flow (and hence maximum endurance) in a jet we need to minimise the product of drag x TSFC.
The drag will determine how much thrust we need and the TSFC will determine how much fuel we need to burn to produce each unit of that thrust.