Why shut it down and not let it run as a static site? Minor CDN costs, even smaller hosting costs, and all that ad revenue is free.

Would you buy an online magazine that is (all assumptions) unprofitable, has negative growth, and not a good brand image?

Brand recognition and pennies on the dollar. I'm really surprised they decided to shutter instead of sell it. It's definitely still worth something.

They could have stop updating news but kept the site alive. Maintenance cost should be negligible.