I think there's a few factors at work here.
Environmentalism emerged simultaneously around the developed world circa 1970. Various "trigger" issues prompted it, everything from dams to toxic waste, but I do find it interesting that it came into being about the same time in most places. This was before the internet and at a time when international travel was far less common for ordinary people than it is today. So less communication but people still started to focus on the environment about the same time.
I think it's no coincidence that this happened just as the West was at its peak economically. If people have money, jobs are plentiful and secure, then they start worrying about things other than the economy.
I suspect we've had what will in hindsight be seen as another major shift in 2008 with the financial crisis. Joe Public is getting poorer, they just haven't really figured out yet what's happened and that it's not a temporary blip. But nonetheless, they're getting poorer and their attention is shifting to economics over the environment. Note that it was in 2008 when the lines on that survey chart linked in another post crossed from environment to economy as the more important theme.
A basic pattern of Western industrialisation, protectionism and the dominance of the US and its' allies with currency ties to gold ran from about 1934 when the Great Depression "make work" schemes got underway to 1971 when it peaked. After that we've had neo-liberal economics and environmentalism which in hindsight I think will be seen to have largely run their course from 1971 to 2008. Both lasted 37 years or about half a human lifetime.
Certainly in my local area, I do perceive that both neo-liberal economics and environmentalism are in decline. Politicians to the Right aren't so keen on the free market as a solution to everything as they once were, they're a little more tolerant of concepts such as public service and state-run enterprises these days, and it's quite some time since we saw a major environmental protest rally take to the city streets.
The world changed in 2008, pretty clearly the "free market" approach slowly but surely pursued since the early 1970's and which became most apparent in the 1980's isn't as perfect as many had thought, and the next crisis whenever it comes will reinforce that. We're now headed in a different direction, it's just not yet clear to most what that direction actually is (just as it wasn't clear in early 1979 what path we were on at that time, it took a few more years for it to become readily apparent to most).
A key point there is that, locally at least, environmentalists were the first to recognise that shift. They proclaimed that manufacturing was dead and the future was in service industries as far back as the 1970's with most thinking they were crazy at the time. But as the factories closed one by one and tourism boomed, it became painfully apparent that they had been right all along.
They didn't cause it, they just worked it out at a time when everyone else was expecting the future to be a continuation of the past. Locally at least, part of the environmentalists' argument always was that whilst their reason for opposition was environmental, it was pointless to build industrial infrastructure (most notably power supply in the local context) if we weren't going to still have factories in business to use it.
Environmentalism is heavily tied up in all of this economic stuff I think. Firstly because it's not too hard to stop something like toxic waste dumping if the factory doing it is closing down anyway. Secondly because it relies on people having wealth to the point that they aren't focused on economics. It gets much harder to pursue such issues if everyone's struggling financially and willing to accept pretty much any form of development in the hope that it puts someone in a job.
The US just had a boom in shale as everyone on this site is no doubt well aware. I'm not overly familiar with US politics, only ever been in the country as a tourist and did the mainstream tourist stuff, but I do think it would likely have been a lot harder for that to occur 20 years ago when "environment" held more sway politically than "economy".
Just my thoughts as someone who sees the environment and economy question as heavily intertwined.