He could resign. That would be "taking responsibility." Just saying you take responsibility isn't actually taking responsibility. Not in a way that matters to anyone anyway.
If he wasn't planning on resigning, he should have just left that bit out of the statement. It comes off as empty and tone def.
Forcing a leader to resign over a bad bet that is not permanently damaging to the company will only make things worse. That leader still has value to the company, and is probably one of the best persons to learn from and fix their mistakes. If you fire a CEO, you throw the stock market into chaos and all of your other leaders become focused on trying to get the CEO job instead of doing their own jobs. You went from one problem to multiple problems.
If he wasn't planning on resigning, he should have just left that bit out of the statement. It comes off as empty and tone def.