So how can a company that's not employee-owned become employee-owned by getting bought by another company that's not employee-owned? The only way that makes sense is if Card Against Humanity was owned by the employees of Clickhole.
Could also just be a philanthropic act for the media attention. CaH have done a lot of advertising through weird (mostly positive) means, it wouldn't surprise me if this was just another example.
I'm a little unclear on the specifics too, even after reading the article. The article says "majority employee-owned company" So Cards Against Humanity still retains some ownership in it I presume.
Here's one possibility: Maybe they bought ClickHole, and gifted over 50% of shares to the employees?