Why did Air Niugini allow Rabaul flight to be overbooked?

Letters, Normal

I would like the management of Air Niugini to tell us the truth about PX 274 to Rabaul and Kavieng on Dec 19.
The flight was already full but there were still many passengers waiting to check in at the counter.
The passengers for PX 274 had waited patiently at the outer gate since 6am, some even arriving as early as 1am only to be told that all the seats have been filled with confirmed passengers.
The question is why did Air Niugini allowed the flight to be overbooked?
If it knew the flight was overbooked, and it knew that there were still many passengers waiting to check in, why didn’t it bother to plan for an additional flight?
The SOS Security did a great job to control all travelling passengers outside until the check-in counters were cleared before letting those waiting outside to enter the departure hall.
I think Air Niugini has a lot to answer on this particular flight.
I am also curious to know why the officer manning the Rabaul-Kavieng counter did not quickly clear the long queue.
Was it because the officer knew that flight was overbooked?
The passengers got frustrated and they started yelling at the Air Niugini officers when the boarding call for PX 274 was made.
Those who failed to make the flight were told to return the following day.
To make matters worse, my children’s hand bag with canned fish, toys and two new umbrellas were removed by the check-in security guards at the departure lounge.
So they called me on the mobile phone to go in and collect the items as they were rushing to board the plane.
When I asked the security guards about these items, they denied any knowledge.
Where are we heading, Air Niugini? -Yakam Kelo Port Moresby