(Reuters) - John Bogle, whose family’s struggles during the Great Depression led him to pioneer low-cost investing and to found Vanguard Group, now the world’s biggest mutual fund firm, died on Wednesday at the age of 89, Vanguard said.

Bogle had been in frail health for years, surviving at least six heart attacks and receiving a heart transplant in 1996. The cause of death was cancer, according to Bogle’s assistant Michael Nolan.

Despite ill health, Bogle was a vital presence through his later years as he pressed for reforms in corporate governance and fund administration.

He often mixed sharp rhetoric with a wry sense of humor and established a reputation as a curmudgeon in his industry, at times at odds with Vanguard executives who eventually stripped him of much of his power within the organization.

Still Bogle, known widely as Jack, kept deep professional friendships and maintained a loyal following through his books and public speaking appearances. Some termed themselves “Bogleheads” in his honor and spread online his messages of thrift and investments in low-fee funds.

“Jack did more for American investors as a whole than any individual I’ve known,” billionaire Warren Buffett said in a statement.

At the 2017 annual meeting of his company Berkshire Hathaway Inc BRKa.N, which Bogle attended, Buffett estimated that by making low-cost index funds so popular for investors, Bogle "put tens and tens and tens of billions of dollars into their pockets."

Slideshow ( 5 images )

Bogle’s life in many ways was the opposite of his great fund industry rival, Edward “Ned” Johnson III, who inherited control of Fidelity Investments in Boston from his father and employed star active managers like Peter Lynch.

Vanguard, in contrast, promoted low-cost index funds, products that Fidelity and the rest of the industry came to emulate.

“He made himself a centurion to the individual investor,” said Charles Ellis, an industry consultant and a former Vanguard funds director. “He had one great message, about lowering fees, and he kept hammering away at it.”

MODEST BEGINNINGS

Bogle was born on May 8, 1929, to a family of modest means in Montclair, New Jersey, and graduated from Princeton University in 1951, working his way through college as a waiter. His economics thesis there earned him a job from an older Princeton alumnus at the Wellington Management Co in Philadelphia.

Bogle rose through the ranks and persuaded the company to start offering more mutual funds, even as he suffered his first heart attack at the age of 31, in 1960. He had a pacemaker installed in 1967 to treat a condition known as heart arrhythmia.

Slideshow ( 5 images )

He created Vanguard in 1974 after a dispute with others at Wellington, and built its products around a new economic model in which the funds would be run by their own directors and staff rather than by an external management company.

In 1976, Vanguard also introduced the first indexed fund for individual investors. According to the company, it was initially ridiculed as "un-American" but now the Vanguard 500 Index Fund VOO.P is one of the industry's largest. Vanguard has some $5 trillion in assets under management, the bulk of it in index funds and exchange-traded funds.

Dan Wiener, who runs a newsletter for Vanguard investors, recounted how Bogle once sued him after he disclosed details of Bogle’s compensation, and said Bogle could have a thin skin about material that did not “paint Vanguard as a virtuous non-profit.”

But Wiener said that when he sent a note wishing Bogle well after a 1996 heart transplant, Bogle responded “in the guise of one of his doctors, who noted that my email had raised his heart rate and that I should refrain from further emails until he was recovered. When I later found out we had a good laugh, at my expense.”

Even as Bogle’s health declined in his later years he remained a combative public presence, arguing that larger fund companies had grown too focused on their own profit rather than serving as stewards of their clients’ interests, including pressing corporations for better governance.

“The mutual fund industry lost its way because of the triumph of managers’ capitalism over owners’ capitalism,” Bogle wrote in a typically fiery passage in his 2005 book “The Battle for the Soul of Capitalism.”