Mr. Kamprad was, like his designer wares, a studied Everyman. He cultivated a provincial openness: curious about everything, but a face lost in the crowd. He was bespectacled and balding, with wisps of graying hair plastered down the sides, jowls and a pointed chin. His blue denim shirts and khaki pants might have been a gardener’s, but there was hard individuality in the dark eyes and compressed lips.

While he lived mostly in seclusion, he traveled to Ikea stores around the world, sometimes strolling in anonymously and questioning employees as if he were a customer, and customers as if he were a solicitous employee. He spoke at Ikea board meetings and occasionally lectured at universities. He rarely gave interviews, but made no secret of his alcoholism, saying he controlled it by drying out three times a year.

To millions of Ikea customers and the general public, he was largely unknown beyond the authorized version of his life and Ikea’s success — his “Leading by Design: The Ikea Story” (1999), written with Bertil Torekull. Its themes had been sounded for decades in Ikea publicity and reiterated in profiles of Mr. Kamprad and the company.

Ikea had been achieved, he said, by frugality: building stores on less costly land outside cities; buying materials at a discount; minimizing sales staff to let customers shop without pressure; putting no finishes on unseen furniture surfaces, and packaging items in flat boxes to be carried away by customers for home assembly (instructions provided).

In 1994, the Stockholm newspaper Expressen uncovered Mr. Kamprad’s name in the archives of Per Engdahl, a Swedish fascist who had recently died. They showed Mr. Kamprad had joined Mr. Engdahl’s fascist movement in 1942, and had attended meetings, raised funds and recruited members. Even after the war’s end in 1945, he remained close to the leader. In a 1950 letter to Mr. Engdahl, Mr. Kamprad said he was proud of his involvement.

Mr. Kamprad responded humbly to the disclosures. In a message to his employees, he said his fascist activities were “a part of my life which I bitterly regret,” and “the most stupid mistake of my life.” He said that he had been influenced by his German grandmother, who fled the Sudetenland before World War II, and that he had been drawn to Mr. Engdahl’s vision of “a non-Communist, socialist Europe.”

Image Mr. Kamprad in 2012. Credit... Fabrice Coffrini/Agence France-Presse — Getty Images

For Swedes, the revelations reawakened disquieting memories of World War II. While Sweden was officially neutral, German troops had traveled across the country from occupied Norway, and an unknown number of Swedes were Nazi sympathizers. After the disclosures, Jewish groups called for a boycott of Ikea, but its business suffered little, if at all, and Mr. Kamprad soon returned to themes of frugality.