Their stated non-profit goal was to benefit all of humanity. Changing OpenAI to benefit their financial backers in a formal sense could be a loss of nearly unbounded value.
Which is probably why they created another, for-profit, entity.
You can argue that it's unlikely the for-profit conservatorship of the non-profit is incompatible with that goal, but legally that becomes very much grey area.
So nothing to loose if their model wouldn't have worked anyway.
And at the current state, its better anyway that China is pushing the non-profit/humantariy aspect of open models.