I wish companies would do away with the "leaving to pursue other opportunities" nonsense and just give no reasons if they don't want to discuss it. No C-level exec resigns "effective immediately" without either a transition plan in place or something concrete lined up. I get wanting to allow him to say he resigned instead of he was fired, but the silly language of the press release just makes it worse.
Maybe “he wants to spend more time with family”?
"Man I hate this place because ____, and I'd rather spend time with my family."
That doesn't preclude wanting to do other things too.