Having taken a peek at the sites source code and seen how it's been built, there's many thousands of lines in one style sheet file alone. Given there are multiple stylesheets used, the size issue you've flagged is likely down to the devs having to wade through a lot of style selectors to tweak them so that they are working for both cursors on desktops and fat fingers on touch devices when making their site responsive.
It can be a time consuming job to iron out all these kind of 'conflicting styles' and with every user having different requirements and expectations [devices, browsers, resolutions etc], subsequently it's not always easy to get right upon first launching it - even if you do beta test it exhaustively before hand!
Given time I'm sure it will be sorted though.
In the mean time I'm trying to hold off sending a list of suggestions for improvements I would make if I were working on this site... e.g. reducing some of the white space - i can see long posts lengths and max post counts per page being heavy on the scrolly finger... :icon_biggrin: