Flybe 1.0 operated EXT-MAN and return twice daily - on occasions three times daily. That enabled day return trips and built a loyal passenger following. It was probably their busiest route out of Exeter.
Blue Islands operated the service 3 days a week with only the one flight. That mean no chance of a day-return and the necessity for a couple of night's hotel accommodation adding to the expense.
I would imagine that such an unattractive offering from Blue Islands has lead to the service's demise.