Well that's an easy one to answer. Status and respect. Status he hasn't earned and respect he doesn't deserve.
These 'valour thieves' or whatever people call them are nearly always men. Infact I don't know of any women, but I'm sure someone will come along with an example. Years ago, I listened to a radio 4 interview with a doctor who had served in the army. He had written a book called something like "why men fight". He said a sentence that stuck with me and really opened my eyes about men and their behaviour. He said "testosterone is the status seeking hormone". I read most male behaviour with this in mind.
With regard to this sort of valour theft, a relative worked for the MOD in the medals office back in the day, and she told me it wasn't uncommon to receive a request for a medal from a family, saying my late dad/grandad took part in/fought at such and such campaign etc but never claimed his medal/s. She said it was always sad when she had to inform them that, erm actually no he didn't, he lied about that. These days it's easy to purchase the medals you want online, and pass them off as your own.
It happens a lot, however this chap is an extreme example and deserves to be punished for it.