Reddit knew this was going to happen if they brought r/place back, right ?

Yes and no. CEOs do have autonomy but in a case like Reddit they are also beholden to the Board of Directors. They make commitments/predictions/projections for the board all toward the ultimate end of working toward a high return on investment for the members of the board and other shareholders. The CEO is then responsible to make these things come true and has autonomy to do things as he sees fit. But if the board has enough power, in any case where they don’t like how the CEO is performing, they will eventually vote to remove him.