There's some warranted skepticism with that premise.

Microsoft was one of the largest software companies on the planet already by 1980 and among the few software companies in existence of any market relevance or development capability that could appeal to a company the size of IBM.

They did $8 million in sales in 1980, $26 million adjusted to 2019. That was a massive software business at the time, and only five years old.

Bill Gates was far richer than his family by 1980, at the age of 25. Microsoft's margins were extreme back then, 40% to 50% on that $8m. Gates was worth $100+ million inflation adjusted by the end of 1980.

That success was accomplished without using family connections to get deals. It's questionable whether Microsoft required help connecting with IBM. Microsoft was already well on its way to being a billion dollar valuation business in today's dollar.

Well, family connections are true, here's excerpt from Bill's mother bio: "Her tenure on the national board's executive committee is believed to have helped Microsoft, based in Seattle, at a crucial time. In 1980, she discussed her son's company with John Opel, a fellow committee member and the chairman of International Business Machines Corporation (IBM). Opel, by some accounts, mentioned Mrs. Gates to other IBM executives. A few weeks later, IBM took a chance by hiring Microsoft, then a small software firm, to develop an operating system for its first personal computer." https://en.wikipedia.org/wiki/Mary_Maxwell_Gates