You're semi-correct about the appointment in my opinion.
Fullarton WAS a grown up when he was offered and accepted the job. He also applied for it in the first place (unless Ray just grabbed him off the street and made him take the job). Both parties were culpable for different reasons. Fullarton should have acknowledged his own limitations and not taken the role, even though he had been offered it. I feel no sadness towards him, in fact I think he was a fool with a huge ego.
On Trew's part, we will never know exactly why he offered the job to Fullarton. It could have been to save a few quid or there could have been other reasons - we will never know, but it was a monumental balls up.
However I see Fullarton's appointment in a different way. There are many football club owners who have appointed managers who they feel have the experience and therefore have a good chance of doing the job well. After a few months, the manager fails and gets the sack. I think Trew was trying something different and took a punt on an untried manager. He soon realised it wasn't working.
Trew wasn't the first and won't be the last. In fact there seems to be a move towards appointing managers who DON'T have a successful record, but instead have the 'qualification'. Again, I feel this is of detriment to English football and personality in the game. Most of these 'qualified' coaches have little or no personality and it is reflected in the type of football their teams play.