Given the risks, it would likely have to be done by a foundation with deep pockets and clout in the community. I could see an org like EFF do the work, they have the clout that any attacks against them would fall flat and they probably have deep enough pockets too.

Besides an org like that that would do it for ideological reasons, the only other party would be some large org that is deeply invested in the WP ecosystem. I imagine there is some ecomm giant that's probably got 8 or 9 figures sunk into WP, for them it would be worthwhile to fork as it would likely be cheaper than migrating to another solution, but that's a hard maybe because you would need the right org with the right set of priorities to take on something like this.

All of this is just pure speculation, if I'm being honest I find it unlikely that either scenario plays out in the real world.

So it’s the end of Wordpress, within a decade if it continues at its current trajectory.

Drupal community to benefit here tremendously. As well as consultant work to migrate away from WP

There's always ways to remove someone completely gone off the rocker. Employees or customers voting with their feet, some big and established name(s) forking off the project, getting the target arrested (if only by provoking an escalation), getting a judge to declare the target mentally unfit, and various illegal methods as well.