How have we ended up with this idiocy?

Well, actually, the reason we've ended up with this idiocy is simple enough. The politicians just didn't take note of what the economists were saying. Another example of how the more the economists are united in a view upon a subject the less influence economists have over it:

Most of the wood fueling converted coal plants in England, Denmark and other European countries is coming from North American forests. Each month, about 1 million tons of tree trunks and branches from southern U.S. pine plantations and natural forests is being turned into pellets and shipped to European power plants, mostly to Drax power station in the United Kingdom.

The growing transatlantic trade is being financed with billions of dollars in European climate subsidies because of a regulatory loophole that allows wood energy to count as if it’s as clean as solar or wind energy, when in reality it’s often worse for the climate than burning coal. Only the pollution released when wood pellets are produced and transported is counted on climate ledgers. Actual pollution from the smokestack — by far the greatest source of carbon pollution from wood energy — is overlooked.

That's a rather large mistake of course. 

And how we ended up here is as simple as we've said above. From William Nordhaus through to Lord Stern the economic analysis said that, if (and obviously only if, whether is not an economic subject) something needs to be done about climate change then the method is to make the one intervention into the price system. Doesn't, on this point, particularly matter whether it is cap and trade or a carbon tax.

But just make that one intervention - do not, whatever else, try to address it piecemeal with detailed regulation of this and that. Because that will be both less effective and also more expensive.

What did the politicians do? Try to plan it all with a series of detailed interventions and regulations into this and that. And that's why dealing with climate change is so expensive, simply because the wrong method of dealing with it is being used.