This often puts a considerable drag on the whole project, one that can easily climb to way above the contributions of that person. Even worse, this is often not visible at the project level, as multiple people start independently avoiding this person, even finding technical work-arounds to avoid working with them; while their direct contributions are visible to everyone, making it seem like they are indispensable.
The situation with Linus is even more interesting: for years people have worked with him knowing that they sometimes have to endure his abrasive manners. Then, one day, enough people seem to have discussed this with him, and he decided to accept their feedback and change his ways. How much more successful could Linux have been had this discussion happened 10 years earlier? How many developers have quit or never started working on Linus out of social anxiety? Perhaps it's 0, perhaps it's not.