If there are less Joules and more people, some people must - by mathematical necessity - be consuming less of them. If your family can still afford to consume the same amount then maybe someone else on the margins is really being pushed.
That is a pretty decent reason for why a large number of people might be getting desperate for political change. It is a stronger explanation than some variant of the more common "maybe they are just really confused and/or hateful and/or unexpectedly stupid". People don't read economic stats but they'll notice if 20% of their electricity goes away.
If you want to point to something, I'd look towards massively inflated house prices (almost 10x over 30 years in some places), and stagnating real wages.
For energy efficiency to cover the change + population growth with no winding back of lifestyles it would need to be something like a 30% increase in efficiency over 10 years, affecting all electrical devices in the country. There is reason to be sceptical that it is a major factor here.
Add to that there is an argument/observation (Jevons's Paradox) that increasing efficiency of using a commodity generally doesn't lead to reduced usage. If it made sense to procure X commodity when it generated Y, it makes it even more sensibly to procure X when it gets you (Y+something).
As for decreasing industrial use ... the default position when a country jettisons its industry is "gee, that might reasonable upset a lot of people and/or cause social problems!". The changes are rather large. Deindustrialising might foreseeable lead to such things as stagnating real wages, as the country can't produce as many goods, or massively inflated house prices as it becomes more difficult to secure useful work/build new houses.
The UK temporarily outlawed older-generation lightbulbs, as well as putting in place a number of measures to reduce energy use. Even Conservatives, historically the party of industry, are now heavily committed towards energy-efficiency measures of all sorts (sometimes excessively so, like the push for those terrible heat pumps).
A decline in energy consumption is a good thing and is absolutely not impacting standards of living in any way in UK society. The reasons for discontent are many, for sure, but not related to energy use in any way. The main issue really is wage stagnation (and hence, availability of time) for the working classes.
The default position when a country's electricity use drops 20% is to be concerned. If they do the same thing 4 more times they will have returned to the stone age.
