This article addresses the published work, but I was interested in more about the technique this article references briefly when it describes blurring the image to .... get a sharper image.
Typically, I'd read the paper, but I haven't taken the time yet. I found an article from last year that might explain the technique more accessibly, and posted it in this community as well: https://steemit.com/hive-160342/@primevaldad/when-imaging-atoms-blurrier-is-better

So, there's the major change they made between 2018 when they first employed the technique, and the refinements they've made since that has created the improvements in the final resulting images.