Former Wall Street Journal tech critic Walt Mossberg's site re/code has a history of Boston's technology business, including this explanation of how the Excel spreadsheet conquered its competition:
Microsoft didn't have the best-selling spreadsheet, didn't have the best-selling word processor, didn't have the best-selling presentation-graphics database. None of (their products) were the leader in the category.
They realized you could shift the purchasing decision from "Is it the best software?" to "Is it the best decision for the company?"; bundle the products together, drop the price from $300 or $500 each to $700 for all of them combined; sell to the top of the organization. And they recognized that they could leverage their operating system.