Yishan Wong's comment here [1] explains it. (He's the unnamed "young up-and-coming" CEO of the story.)

In short, the plan was to reduce Condé Nast's ownership of Reddit by hiring a new CEO, and convincing that person to demand, as a condition for their hiring, that CN reduce their ownership share. Further VC funding and back-room machinations let them further reduce CN's share of the company, thus eventually wresting control over Reddit back to the original founders. Yishan was subsequently pushed out and Ellen Pao promoted to CEO, which didn't go so well either.

Both Altman and Pao are responding in that thread.

[1] https://www.reddit.com/r/AskReddit/comments/3cs78i/comment/c...