There are thousands of magazines published in the world to meet the needs of different readers. But only a few of them are influential world-wide.
You have hit the point. It's really hard for a magazine to be well known to people of various ages and educational backgrounds.
But I think Digest is supposed to be the top one. Its subscribers or buyers are from all social classes, perhaps, a majority of them from the educated group. It's quite strange that the readers love it after reading it.
To my mind, the success of Digest is in the clever selection of its articles in each issue.