Theoretical possibility then:
You still use that personal email in the same browser? That means you visit Yahoo website, which can set some cookies identifying you, including third-party ones (advertising/tracking), if those are not blocked by Safari. The same tracking cookies can be used by Tradesy, so that site can tie your visit to your Yahoo identity.
I actually use the Apple mail client, so I get my spam mail and my personal mail in the same interface. My angry deleting of cookies and web history following the Criteo email would have cleared any log ins, but I haven't used the yahoo mail web interface for many years. However!! I remember going to flickr briefly about a month ago, and since it is a yahoo service, it would have been connected to my personal yahoo ID/email address (correct?). It's possible that I never logged out, so could it have mined my address that way? I am still incredulous and outraged that Criteo could use this to mine my address and spam me, but this could be how they got my personal email/yahoo ID.
Thank you so much for your insightful comments and for "investigating" with me! Even though this is still somewhat mysterious, I've learned from this and also discovered my ghostery settings were off which was very valuable. Now I just have to figure out how to block Criteo and similar invasive species. I may have to go off the grid after all.