A good starting point for this question would be this famous discussion: https://en.wikipedia.org/wiki/Tanenbaum–Torvalds_debate https://en.wikipedia.org/wiki/

A good starting point for this question would be this famous discussion: https://en.wikipedia.org/wiki/Tanenbaum–Torvalds_debate https://en.wikipedia.org/wiki/Tanenbaum–Torvalds_debate Which in a nutshell comes down to Linus's view that producing a system that meets current needs (for example by offering a simple API) and is reasonably performant -- even if it ran on but a single architecture such as the i386 -- was more promising than a design offering "theoretical" benefits (such as portability) but which either didn't deliver the goods today or just wasn't reasonably performant. This is a vast simplification of a much broader set of issues but if one digs into the notes of why subsequent projects (e.g. Windows NT) moved away from microkernel designs, or the roughly analogous microservices debate of the past decade -- one often finds echoes of the same basic considerations.