Bill Campbell in undated photo (Intuit via AP)

Bill Campbell, a widely admired coach and mentor whose homespun advice on leadership and management nurtured a range of Silicon Valley luminaries including Apple co-founder Steve Jobs and Google co-founder Larry Page, died April 18 at his home in Palo Alto, Calif. He was 75.

The cause was cancer, his family said in a statement.

Although he wasn’t widely known outside Silicon Valley, Mr. Campbell played a pivotal role in shaping the direction of both Apple and Google, two of the world’s most powerful companies.

The gruff, bear hug-dispensing Mr. Campbell worked at Apple as a marketing executive in the 1980s and was appointed to the Apple board when Jobs returned to the company in 1997. He was chief executive of financial-software firm Intuit for five years in the 1990s and served as its chairman until January.

But it was as a leadership coach, power broker and behind-the-scenes mentor that Mr. Campbell made his real mark in Silicon Valley. Pridefully non-technical, he was fondly referred to as “the contentless leader” by some of the executives who worked with him because he rarely delved into the details of a company’s technical problems or business model.

Prompted by Kleiner Perkins Caufield Byers, a venture capital firm, Mr. Campbell worked with former Google chief executive Eric Schmidt and company co-founders Page and Sergey Brin to help them work out their early differences and eventually forge one of the most successful partnerships in corporate America.

The former head football coach for Columbia University from 1974 to 1979 (overall record: 12-41-1) had an intuitive feel for how talented, driven people could work together in highly pressurized environments. The list of executives who worked with Mr. Campbell is long and includes former eBay chief executive John Donahoe, ex-Twitter chief executive Dick Costolo, Schmidt, now executive chairman of Google parent Alphabet, and many of the tech world’s leading venture capitalists.

“I would argue that Bill has had a bigger impact on Silicon Valley than any other single person simply because his reach was so amazingly wide,” Bill Gurley, a partner at venture capital firm Benchmark, wrote in an email. “He [influenced] so many people from Steve Jobs down to eighth graders on the Sacred Heart flag football team. Bill inspired greatness. He helps everyone be better.’’

Mr. Campbell often found himself at the center of Silicon Valley’s most sensitive battles between outsize personalities. In 2011, when Jobs started railing against onetime ally Google for developing the Android mobile operating system to compete with Apple’s iPhone, Mr. Campbell advised both companies and was caught squarely in the middle. He somehow walked the tightrope and maintained both relationships.

Jobs and Mr. Campbell were particularly close, said Mickey Drexler, the chief executive and chairman of J. Crew who had served on Apple’s board with Mr. Campbell. He said Jobs sought Mr. Campbell’s advice on the most important issues facing Apple, and admired his experience and frankness. “He never had an agenda,” Drexler said. “He spoke his mind, whether it was in the boardroom or outside the boardroom.”

Mr. Campbell spent most days with Jobs, who died in 2011, during the last year of Jobs’s life and would walk with him around his Palo Alto neighborhood. He also advised Jobs’s successor, Tim Cook, and then left the Apple board in 2014.

William Vincent Campbell Jr. was born in Homestead, Pa., near Pittsburgh, on Aug. 31, 1940. He graduated in 1962 from Columbia, where he also received a master’s degree from the Teachers College in 1964.

He was an offensive guard and captain of the football team that won an Ivy League championship in 1961. The National Football Foundation annually awards the William V. Campbell Trophy to the best scholar-athlete in the nation. (He later chaired Columbia’s board of trustees.)

After his coaching stint at Columbia, he was a vice president at the J. Walter Thompson advertising agency in New York and also worked as general manager of consumer products for Eastman Kodak in Europe. He joined Apple in 1983.

In the late 1990s, Amazon’s board dispatched Mr. Campbell to Seattle to confront its hard-driving founder and chief executive, Jeffrey P. Bezos, and to determine whether he should step aside for his more experienced chief operating officer, Joseph Galli, a former executive at Black & Decker. Mr. Campbell later said he came away convinced Bezos, who owns The Washington Post, “was just the right guy for the CEO role.”

Donahoe said his decision to step down as eBay CEO last year after the company split from PayPal was influenced by Mr. Campbell. Donahoe was close to Mr. Campbell, who advised him on major decisions and coached flag football for the four Donahoe children. “You’d go to his house; you’d talk for 45 minutes; he listened,” Donahoe said. “He probed, and he’d tell you, ‘I love you to death, and I’m going to tell you the truth.’ Then he’d give you his reaction.”

Mr. Campbell was a part-owner of the Old Pro, a sports bar in downtown Palo Alto, and once a month would hold beer and pizza sessions that brought together an eclectic mix of wide-eyed young entrepreneurs and his older, crustier friends.

His marriage to Roberta Spagnola ended in divorce. Survivors include his wife, Eileen Bocci Campbell; two children; and three stepchildren.