I'm still going with the theory that he was on one of those pedo trading networks, but was just one of those guys downloading and re-uploading said underage porn, and was not involved in either running these networks nor producing any videos.

I think there's also a fair chance that these videos involved teen girls over 14, and not the outrageously sick shit involving 8-year-olds or whatever.

He probably got nailed in one of those stings, and then was able to strike a probationary deal because his role in the entire thing was small, and they figured they'd take the sure-thing conviction instead of rolling the dice in court against basically an internet downloader/uploader.

I highly doubt this was a case where he accidentally clicked on some link on a shady site and ended up with child porn on his machine.

At the same time, as has already been pointed out, there's no way he's only getting probation if he were a major distributor of child porn.