Just as senators from both parties were agreeing Wednesday night to roll back banking regulations put in place after the financial crisis, a pair of debt-driven business failures hit the headlines — as if to remind us why Congress tightened rules in the first place.

Toys R Us, that iconic emporium of fun, said it would be closing all its stores, and, shortly afterward, the radio giant iHeartMedia filed for bankruptcy. It looks like the latest iteration of a familiar story: Old-school businesses lose out to new platforms — Toys R Us against online giants like Amazon, iHeartMedia against podcasts.

But that’s just part of the story.

In both cases, old debt was as important as new competition, with the trudge toward failure traceable to the prerecession years of the mid-2000s, when debt was all the rage among homeowners, banks, and private equity dealmakers.

Toys R Us was bought by private equity firms in 2005; iHeartMedia was acquired in 2008, with Boston’s Bain Capital and Thomas H. Lee Partners teaming up for the purchase. And, as is common with private equity deals, borrowed money played a big role.

That’s how private equity firms usually operate, financing their purchases with large loans from banks and investors. That burden then gets loaded on to the companies, which must figure out how to repay creditors.

Both deals were done during the giant debt bubble in the middle of the last decade, when banks and investors climbed over each other to lend money with better repayment rates than were available in the bond market. Of course, then came the mortgage bust, the Wall Street bailout, and the stock market’s brutal sell-off.

In the case of Toys R Us, the retailer was left with roughly $5 billion in debt that has never gone away. Year after year, the company has had to pay roughly half a billion dollars just to finance that debt, limiting its ability to invest in operational improvements.

IHeartMedia racked up a staggering $20 billion in debt since its buyout, and, over the last five years, the cost of servicing that debt has actually exceeded the company’s earnings.

Limiting these kinds of leveraged buyouts has been a key regulatory focus of the Dodd-Frank rules put in place after the financial crisis of 2007-08. Banks were discouraged from participating in highly leveraged loans, and they seem to have listened. Which is not to say the solution was perfect; where banks stepped back, other, less-regulated, shadow lenders have come forward to support private equity deals.

So is Congress working to tighten the rules on these shadow lenders — enforcing a stricter debt limit for private equity purchases or looking for ways to block nonbank funding sources? No. If anything, lawmakers are moving in the opposite direction.

On Wednesday, 16 Democrats joined with Republicans to roll back oversight on all but the very biggest banks, meaning that if this bill becomes law — as expected — many regional and national banks will be allowed to take on more debt, with less stringent oversight and less regular stress tests.

There isn’t necessarily a straight line from this bill to the world of leveraged buyouts. But the very fact that Congress is undoing parts of the Dodd-Frank Act reflects the deregulatory moment in which we find ourselves. With the financial crisis receding from view, and the economy humming, tight financial regulations seem less urgent — and concerns about excessive bank lending less pressing.

But the zombie-life and ultimate collapse of Toys R Us and iHeartMedia provide a reminder of the lasting risks that come with easy bank lending and rising corporate debts. Bad deals, built on unmanageable debt, may boost prospects in the short term, but they can leave behind crippling, long-term burdens.

When that happens to a few companies, it’s a warning. But the real concern is that it could afflict the economy as whole, allowing business and household debts to balloon until they pop. That’s not a theoretical risk; it happened just a decade ago.

Evan Horowitz digs through data to find information that illuminates the policy issues facing Massachusetts and the United States. He can be reached at evan.horowitz@globe.com. Follow him on Twitter @GlobeHorowitz