How did they make it through officer candidate school in the first place?
To tell you the truth I am not an expert on the Marine Corps but they may have come right out of ROTC.
In the Air Force we ROTC grads were officers as soon as we graduated and swore in and I think that is the same way it works for all the other Services. OCS is for the folks who earned a degree but did not go through ROTC or the academies.