My honest best guess as to what did it -> When @deray complained. Chuck tagged his handle in the tweet, and because Deray could honestly claim it was a threat directed towards himself the automated reporting bot finally big footed that complaint straight to a human being for confirmation, et ouilla Chuck was suspended.
In other words, just like before none of the thousands of other complaints people made mattered one whit. Twitter only really gives a shit when the target of harassment or violence files a report themselves.