That's an amateur job. Resin explains it - you try to do some exfiltration via an external commercial service? Come on.

If the author had setup an encrypted partition where all the "real stuff" was found, and the key for such partition was in-memory only, possibly going alone one of the small rpi UPS/batteries to prevent minor electrical hiccups to make the whole operation fail.... it would have been almost impossible to get back at the author.

Also, using a nice "black box" that looked like a sort of electronic device, instead of some randomly put together rpi+pieces, would have made the device mostly invisible.

So: an amateurish hacking job.