Because there's an ideology that wants a return to a "simpler" age and is willing to defend its inevitabily.

Why is it so hard to understand this!?

Three things:

1. "It is difficult to get a man to understand something, when his salary depends upon his not understanding it!". Add to those numerous beneficiaries of the fossil fuel industry those who actually do understand the problems with continued reliance on hydrocarbons but don't care about the consequences and go to great efforts to deny and spread uncertainty about the problem. This leads us to:

2. The massive PR campaign funded by these people and the stultifying effect it has had on public opinion. This is buttressed by the deliberate strategies employed to make politics repugnant and drive down participation and all of the hot button 'social issues' such as abortion, gay marriage, gun control, etc. which has served to distract and divide in addition to polarizing. This brings us to:

3. The whole structure of 'inverted totalitarianism' that has grown up in the USA but which has been 'globalized' right along with its chief instrument - financialization. The USA and the UK have the improved, post-modern apparatuses of a pre-WWII totalitarian state such as Nazi Germany or the Soviet Union, but without a supreme leader. Instead we have a vastly improved form of oligarchy where the individual players in the political system are irrelevant and replaceable and power is exercised by corporations through the financial sector and through the military/security state/mainstream media complex. The top leadership positions in this oligarchy are similarly replaceable and the potential candidates are sufficiently aware of the common interests of the oligarchy so as to create a stable system.    
   

"It is not necessary to have hope in order to persevere."

Because it's not actually true?

The official ET line is 'Do renewables, raise taxes to redistribute wealth, and everything will be fine."

Consider the possibility that perhaps there's more involved, and the post-war boom was created by a number of distinct circumstances that either don't apply now or only apply partially. Specifically:

1. A relative energy glut leading to cheap energy. (I'll agree with the premise of the original piece here. I think it makes a difference - but I'll add that this not only makes economic activity possible, it also creates faith in the future, because it's possible to believe that your business isn't going to get the rug pulled out of it. It's much harder to believe that now, because the oil price crash is temporary and renewables aren't fully established yet.)

2. Good local infrastructure that can make use of available resources. The US freeway system made it easier to think about shipping physical items nationally. Globalisation hadn't happened yet, so the economic activity stayed inside the US and Europe. This gave labour more local bargaining power, which raised wages. Now that globalisation has happened, labour competes internationally, which is very bad for everyone.

3. A research-led culture in science and engineering, supported by trophy-project national policy (see also Manhattan Project, Internet, Concorde, the Space Program, and others). This is a huge deal. It was deliberately created during WWII, nurtured further during the Cold War, and then it was thrown away during the financialisation of the 80s.

4. Low-hanging fruit in science and engineering. Aerospace, nuclear power, and computing (after Turing) were relatively accessible. Today we have quantum computing, which is hard, fusion, which is hard, and wacky hypothetical starship drives, which are somewhere between really, really hard and impossible.

5. A compliant population inspired to consume by propaganda marketing. This is still true today. But because of the wage squeeze personal wealth has crashed for most of the population.

Bottom line is you need a combination of circumstances to create a boom. Spending tax money on its own probably won't do it, because the money will either flow out of the country, or it will end up pushing up prices of essentials (e.g. rents from property) without creating new kinds of economic activity.

There's certainly a case for Keynesian pump priming which can create infrastructure (physical and intellectual) that can sow the seeds for a boom in a decade or two. But it's not an instant fix, and it needs policy decisions that understand the return will take a while.

Obviously we've had the opposite of that, with financialised policies destroying future growth prospects. But I don't think throwing money at the problem ten years ago would have done any more than provided a quick and very temporary growth blip.

The Energiewende could have been a terrific Keynesian stimulus, but they messed it up by making consumers pay for it, which gave them an excuse to kneecap it subsequently.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}

There are economies that are substantially following the Keynes 'euthanasia of the rentier' disideratum. Most of them are BRICS, where government controled public banking is predominant and there is cheap credit for needed infrastructure and industry. This, of course, is anathema to western oligarchies and their minions such as the IMF and the World Bank. It is not just the different stages of development that is responsible for the differing growth rates between the BRICS and the 'developed world'.

"It is not necessary to have hope in order to persevere."

The Prudent Bear: Malthus was just 220 years early (Martin Hutchinson)

The average earnings of U.S. men between 25 and 34 with only a high school diploma have fallen 25% since 1979, according to Census Bureau data. Women in the same category have done better, but their earnings also have fallen. Given that GDP per capita has risen 73% in real terms since 1979 on World Bank data, those are shocking statistics. Their implication is that the value of the labor of people with ordinary skills has gone into a deep decline even as the country and the world has gotten richer. In other words, Thomas Malthus' gloomy prophecies, written in 1798, were not wrong. They were merely early.

[...] If a Malthusian problem were to occur, we would expect it to occur first in the rewards of modestly skilled people in the world's highest-cost labor markets, because their work is most easily substitutable and can be undercut by emerging market labor. That appears to be what is happening. In the U.S. at least there is a supply surplus of modestly-skilled workers, driving down wages. Since the labor-participation rate in the workforce has dropped sharply since 2008, and these statistics include only workers who are employed, there is clearly a major supply-demand imbalance.

A provoking clutter talk on globalization, financialization, resources, technology follows.

There is another solution: drastic reduction of population (over whatever period is necessary to accomplish this through incentives and without coercion). If the world's population were one billion instead of eight billion, the amount of land and resources available per unit of labor would be octupled and the environmental damage caused by production would be reduced by seven-eighths. Similarly, the amount of capital available per worker would be greatly increased (albeit probably not by a factor of eight), while the knowledge base per worker would octuplet (although the rate of adding to it wouldn't). With labor suddenly scarce, even at the modestly skilled level, the returns to labor would be greatly increased.

That must be the arithmetic.