I think the ranting and swearing help -- they make him more memorable, and therefore more generally well-known. This can then feed on itself a bit to make him more of a public "celebrity" and have more pull than he would otherwise.

I agree that his other skills are likely more important overall, and there are certainly other ways to be memorable, but I don't think you can discount the contribution of the ranting.

Without the swear words this wouldn't get as much publicity as it does, and that may help in getting Intel to change.

Linus' swearing falls in line perfectly with the FOSS movement -- to not conform to corporate hierarchy and societal norms.

Like others said, his language helps drive the point home and leaves more of an impression. It also humanizes Linus as well.