Five days after a train carrying crude oil derailed and exploded in Lac-Mégantic, Quebec, the rural town resembles a scene of desolation. Its downtown is a charred sacrifice zone. 50 people are likely dead, making the train's toll one of the worst disasters in recent Canadian history.

In the explosion's aftermath, politicians and media pundits have wagged their finger about the indecency of "politicising" the event, of grappling with deeper explanations. We can mourn, but not scrutinise. In April, prime minister Stephen Harper even coined an awkward expression – "committing sociology" – to deride the search for root causes about horrifying events, in the wake of an unrelated, alleged bombing attempt.

But to simply call the Lac-Mégantic explosion a "tragedy" and to stop there, is to make it seem like an accident that occurred solely because of human error or technical oversight. It risks missing how we might assign broader culpability. And we owe it to the people who died to understand the reasons why such a disaster occurred, and how it might be prevented in the future.

So here's my bit of unwelcome sociology: the explosion in Lac-Mégantic is not merely a tragedy. It is a corporate crime scene.

The deeper evidence about this event won't be found in the train's black box, or by questioning the one engineer who left the train before it loosened and careened unmanned into the heart of this tiny town. For that you'll have to look at how Lac-Mégantic was hit by a perfect storm of greed, deregulation and an extreme energy rush driving companies to ever greater gambles with the environment and human life.

The crude carried on the rail-line of US-based company Montreal, Maine and Atlantic Railway – "fracked" shale oil from North Dakota – would not have passed through Lac-Mégantic five years ago. That's because it's part of a boom in dirty, unconventional energy, as fossil fuel companies seek to supplant the depletion of easy oil and gas with new sources – sources that are harder to find, nastier to extract, and more complicated to ship.

Like the Alberta tar sands, or the shale deposits of the United States, these energy sources are so destructive and carbon-intensive that leading scientists have made a straightforward judgment: to avert runaway climate change, they need to be kept in the ground. It's a sad irony that Quebec is one of the few places to currently ban the "fracking" used to extract the Dakotan oil that devastated Lac-Mégantic.

But fossil fuel companies, spurred by record profits, have deployed a full-spectrum strategy to exploit and carry this oil to market. That's one of the reasons for a massive, reckless increase in the amount of oil shipped by rail. In 2009, companies shipped a mere 500 carloads of crude oil by rail in Canada; this year, it will be 140,000.

Oil-by-rail has also proved a form of insurance against companies' worst nightmare: a burgeoning, continent-wide movement to block pipelines from the Alberta tar sands. A group of Canadian businessmen is pursuing the construction of a 2,400-kilometre rail line that could ship 5m barrels of tar sands oil from Alberta to Alaska. Companies are also trucking it and entertaining the idea of barging it down waterways. This is the creed of the new energy era: by any means necessary.

The recklessness of these corporations is no accident. Under the reign of neoliberalism over the last 30 years, governments in Canada and elsewhere have freed them from environmental, labour and safety standards and oversight, while opening up increasingly more of the public sphere for private profit-seeking.

The railway in Canada has hardly been exempt. Up until the mid 1980s, the industry, publicly-run, was under serious regulation. By the time the Thatcherite Progressive Conservative prime minister Brian Mulroney was finished with his reforms, it was deregulated, and companies had rewritten the safety rules. That launched an era of cost-cutting, massive lay-offs, and speed-ups on the job, and eventually, the full privatization of companies and rail-lines.

The Liberal government completed the job by turning over what regulation remained to rail companies themselves. A report issued in 2007 by a safety group spelled out the result: Canada's rail system was a disaster in the waiting.

It's little wonder, then, that today's oil and rail barons have cut corners with ease. They've been using old rail cars to ship oil, despite the fact that regulators warned the federal government they were unsafe, as far back as 20 years ago. A more recent report by a federal agency reminded the government that the cars could be "subject to damage and catastrophic loss of hazardous materials." All were ignored. To top it off, the federal government gave the go-ahead last year to Montreal, Maine and Atlantic Railway to operate with just one engineer aboard their trains.

All of which means it will not suffice to find out if a brake malfunctioned the night of the disaster, or limit ourselves to pointing at the failings of lax regulation. The debate should be about the need for another kind of brake, over the mad pursuit of infinite resources, and the unshackling of reckless corporations, on a finite and fragile planet.

Canada's political class will not be pleased by the lessons to be drawn. The government needs to get back into the business of heavily regulating corporations – through incentives, through taxes, and through sanctions. And this will involve not just grappling with the dangers of the transport of oil – which will remain unsafe, whether by rail or by pipeline – but starting a rapid transition away from an extreme energy economy entirely. That will not happen as the result of any government inquiry, but a noisy social movement that puts it on the public agenda.

That's why the most fitting response to Lac-Mégantic actually happened two weeks ago, by US residents 100 miles across the border in Fairfield, Maine. They were arrested blockading a train carrying the same fracked oil from the same oilfields of Northern Dakota, to the same refinery in New Brunswick, Canada. Their message was about ending our reliance on oil, not soon but now. For those who never knew the victims of Lac-Mégantic, there could be no better way to honour them.

• Follow Martin on Twitter: @Martin_Lukacs