Because there are less people reading the Times, fewer publicists are directing people to be interviewed at the Times. If you know people are reading the Guardian and not the Times and you want to get your message out, you go to the Guardian because more eyes are going to see your message. That is going to set up a feedback loop where people say "hey, the guardian has more content than the Times does, why am I reading the times." Then fewer people produce content for the Times, fewer people read the Times, etc etc etc.
It is hard to develop a user base when you seem to be actively driving away readers and by extension the people who develop your content.