The way you worded this has me imagining the counterfactual world where lots of people traded Bill Gates a linker for a compiler.

Compilers cost real money back then. Word got out that this was how you got a free compiler. You just wrote a linker, and you got in touch with Bill and offered it to him. (You did have to write your linker in a single huge file of assembly, because you didn't have a compiler or a linker yet. It was fine, more programmers knew assembly back then.)

Microsoft has thousands of linkers. They're the linker company now.

Most of their other products started as test cases for their linkers, that they also happen to sell separately as a side business because why not.

Excel is a notable exception, because due to a series of overengineering decisions, it actually is a linker that gradually gained spreadsheet features.