The difference between your first draft and mine is that I've only included links where each site had at least 1% of users in the other site. This helps make links more meaningful.
For instance, about 37k users were members of both Tumblr and Plex. Tumblr had the largest number of Plex users, so it should be a strong link, right? No: because Tumblr has such a large userbase, this is a relatively insignificant relationship; 0.14% of Tumblr users had Plex accounts, which ranks only 20th for Plex.
Compare this to Plex and Xbox-Scene. 5.6k users had Plex and Xbox-Scene accounts, which is about 2% of each site's userbase. I believe this link is much more meaningful than the Plex-Tumblr link, and I believe my visualisation bears this out.
* Note: since I ignored all lines with only one site, this "1%" only includes users who were in more than one breach!