Every single failed manager ever can give reasons why it didn't work in certain situations and Neville's greatest skill appears to be convincing people that because he's good in a studio he will be good on a bench. However the simple FACT is, he has failed in 100% of his managerial jobs.
It's not just giving reasons though.
The players already had too much control at Valencia so it wouldn't have made a difference who went in - they only wanted their pay.
The language and culture another reason.