I have no idea what I did wrong other than use this extension. Hopefully future versions of this extension will adhere to the Google Adsense ToS so this doesn't happen to anyone else.
Topic on Extension talk:Google AdSense
Did you click on the ads yourself? That seems to be the reason for a lot of suspensions.
As indicated by a discussion on the Google Product forums, the extension shipped with code that's against Google's policies by default. Maybe that was why.