The power grids were not standardised even on voltage, frequency or even a.c/d.c and as such was highly decentralised.
Steam was still very much in evidence, especially in rural locations and was used to provide power for many machines. Steam was also used in factories to operate group shaft drive machines - you will have seen those old photos of factories where everything was running from overhead rotating shafts, which in turn were connected by pulleys to various machines. The prime mover in many such factories would often be a steam driven motor, or occasionally a single large electric motor that might itself be operated from a steam driven generator.
As such, coal was probably more critical, though fuel oil could also be used. Railways were far more extensive and very difficult to put out of action for any significant length of time, canals were extremely difficult to put out of action, rivers were virtually impossible to compromise, and all these made the movement of bulk fuels possible. Add to all this; precision bombing hardly existed, was generally extremely risky and reserved for specific high value targets instead of more general infrastructure degrading.
Allied aircraft simply could not carry out daylight raids to hit smaller targets such as power stations, power lines or even rail lines and canals, the losses were far too high.
The article also notes that any such vulnerabilities of the German power distribution system were only identified once the war was over - we can all be wiser after the event. It was noted for example, that the heavy bombing campaign might well have been much more effective and result in much lower allied losses had medium and light bombers such as the Mosquito had been used, but again that was identified well after the war was over.
There were tactical errors regarding the use of bombers, which should have been used far in a far more targeted manner, instead of area bombing, but it took several years before tactics developed to such a degree that a useful predictable and provable effect could be meted out and measured.
I think the author is really stretching things here - I note they don’t mention the failure of the German campaign on London which failed even to put out of action the docklands area, and this was a much easier target to identify and hit with relatively light casualties.
Heavy bombing was a relatively new technique, it had proven very effective in Spain with medium bombers, and it had been thought that heavier bomb loads would be proportionately more effective.