How the NSA Identified Satoshi Nakamoto
medium.com
medium.com
Also it is very hard to imagine that the implementation details would be that simple. Seems like he has the same template when he wrote his licence plate scanning story.
TL;DR, analysis of writings attributed to him/her/them, cross referenced with data from mass surveillance.
I don't see why this has to be limited to the capabilities of an intelligence agency. Perhaps they have the motive, but I'm sure private citizens could perform the same data mining queries (without mass surveillance).
Either way, this post presents zero information and just unsubstantiated speculation.