Google soft-forked Linux for Android (maintained in parallel IIRC) but re-merged into the mainline, presumably because why maintain a whole operating system?

In theory the Linux Foundation would keep Google, Microsoft, AMD, whoever playing nice with each other for mutual benefit and maintenance of Linux, but like you said, and the source of my worry, is who else would have Linus’ combination of prestige, principles, and perseverance?

I’m sure there are others who could fill the role, but even Linus is still bullying Nvidia with only partial success. The most vital role Linus probably has had for some time now is leadership. But even someone who might have superior soft-skills wouldn’t have the history, which certainly contributes to his authority.