So it's seriously a statement of fact that he's the only person in the entire community who could possibly debug that problem? I find that incredibly hard to believe.

If there were someone else, it sure sounds like he would be happy to have sloughed off the work. It doesn't sound glamourous. It sounds like it sucks. So everyone else would rather work on something they think is cool, and Linus is stuck with the crap work that in the end nobody is willing to do. That is why he's the guy in charge. That is why he deserves the credit for Linux.

Not "could" - "will". It's not the same thing.