Probably did it as a future young constable trying to impress and as he rose through the ranks he has had to live with the lie as there was no going back.
Even when found out his attempts to garner sympathy and transferring those ribbons to his right breast is still in a way a continuance of that lie, as the relatives that actually earned the awards are still living, so he still isn’t rightly entitled to wear them and even if they were not living, they were only supposed to be worn on the likes of remembrance days.
The decent thing to have done would have been resigned, as if he is sacked one wonders if his pension etc will be preserved, bearing in mind his promotions etc could have been swayed by his character and past history that is now in doubt.
It does as said earlier bring into question their vetting procedures.