I don't think CityJet was ever a good prospect for SEN. They are a business airline with a reputation for high fares which is exactly NOT what SEN's market is.
Flybe are established, and have a presence in the area, plus this was Stobart control everything and make a margin at every step of the way.
Personally, I think it could be good, it could be good for the SEN, and also good for the airline, providing growth and possible new equipment ... interesting times I think