Actually the loads were pretty good on the Dash 8 the last time the route operated, same for Bristol, but they were dropped to accommodate extra flights to Leeds and East Midlands. At the time I guess a combination of not having enough airframes, having the monopoly between NI and LBA (Jet2 dropping their service around the time), having more connectivity through MAN than LPL, the setting up of EMA as a small hub (connections to AMS etc.) helped in the decision.
Hopefully with the introduction of 'new' Dash 8s, the current recruitment program, and with the business seemingly turned around (or in the process of being) the route will stay. Liverpool is popular for the footie fans going there, or to Manchester, and a bit of healthy competition against Easyjet is good for us customers.