In the late 1960s, while fledgling new retailers Walmart, Kohl's, Kmart and Target were hard at work establishing a foothold in the hearts, minds and wallets of the American consumer, the nation's dominant retailer was busy building the world's tallest building.

In pouring its funds and focus into Chicago's Sears Tower, America's original super-store may have unwittingly become the architect of its own long, slow and painful demise.

“Walmart, the strongest of all those four, wasn’t anywhere near where Sears was for a couple of decades," says James Schrager, professor of entrepreneurship and strategy at the University of Chicago's Booth School of Business. "So, if Sears was on top of things, even in the early 80s, they could have been Target or a better version of Kmart, they could have been any of that. But they sat on their hands and built their tower in 1969 instead.”

It's been a precipitous fall for the one-time retail powerhouse, which this week filed for bankruptcy after years of losses.

Established 123 years ago, Sears was literally the place where America shopped, as its tagline boasted.

Sears had everything from clothing and toys, to tools and appliances. It even sold housing kits. Thousands of Sears homes still stand across America today. For decades, American families eagerly awaited the delivery of the retailer's several-inches thick mail order catalogues.

The secret to Sears' success was being able to stay ahead of the market, according to Schrager.

From small stores in small towns, to big stores in downtowns in the 1920s; to a thriving catalogue business for smaller outposts, the main way America shopped right through to the 1950s and 60s; and then the switch to anchor stores in shopping malls through the late 1970s, Sears was always on the move, changing with the times.

But then the retailer seemed to stop evolving.

While the Walmarts and Targets of the world recognized the value of moving away from shopping centers and opening massive spaces in strip malls where customers could park right in front of the store, Sears stayed at the mall.

The competition also developed individual identities and expertise. Target became known for its upscale, fashion-oriented approach, Walmart for superior logistics in smaller towns, and Kohl's had fashion-only soft goods, says Schrager.

Meanwhile, Sears seemed to lose its focus.

“Sears slowly lost track of its retail business by being fascinated with other things," Schrager says. "In 1969, they began to build the tallest building in the world, that took a lot of time away from the business. They bought a stock brokerage company, which they had no business doing. They bought a real estate company, which they had no business doing. They developed a wonderful credit card called Discover, which has nothing to do with retailing."

And along the way, the type of people at the top, the people making the business decisions, changed.

“Merchants are the lifeline of the business and Sears allowed them to wither," Schrager says. "How do we know that? Because, after a while, Sears wasn’t getting a merchant to run the business. They were getting a financier or a marketer or someone other than a dirty-fingernails merchant who spent their life trying to beat the merchant down the street.”

Edward Lampert, Sears' most recent CEO and majority shareholder, is a hedge fund billionaire. He took over in 2013 and expressed hopes of turning the company around.

Although Sears just filed for bankruptcy protection this week, Schrager believes the final death blow for the retailer occurred back in the early 1990s.

That's when previous company executives decided to sell off the profitable parts of the business, while keeping the failing stores. In 1993, Sears shed the Discover credit card, its real estate company Coldwell Banker, and its Dean Witter Reynolds stock brokerage. Allstate, its insurance company, followed in 1995.

“There’s nothing left. Retail walks by you," Schrager says. "You can’t stand still, and Sears has been standing still since 1969. That’s a very long time. The world has evolved two of three times since then…it’s over."

While one-time competitors like Walmart, Target and Kohl's continue to change and thrive, Kmart, which is now operated by Sears Holdings, is also in financial trouble because, Schrager says, it too failed to change with the times.

As for the one-time king of the pack, the next time consumers get excited about buying something at Sears could be when the bankruptcy court rules that the place where America once shopped must itself now be broken apart and sold off for the best possible price.