I think that in a nutshell, when we were preserving meat 100+ years ago the life expectancy was down in the late 50s at best.
As MS is disease that occurs for the most part in middle-age, most of those people eating preserved meat 100+ years ago would have been dead anyway before they had chance to develop MS in the first place!
EDIT - I had assumed it was this article you were referring to!
http://www.bbc.co.uk/news/health-21685022