That's true for everything. Apple wouldn't have been apple without Woz, but I'd argue Jobs had a much bigger role in making apple what it is. Similarly, Linus is the one who has built and shaped Linux into what it is today. Other people have of course contributed, but they haven't influenced Linux in any way. If not for these specific people, some others could have contributed and we'd have the same result today. But you cannot replace Linus like that.