There must have been a reason they left Malaga (was it 2012)? Although back then it wasn't the most popular of destinations. It's grown massively over the last three or four years with Marbella and other resorts seeing a huge rise in tourism and popularity. The flight market was and still is saturated to Malaga and perhaps TCX/MT wanted to utilise aircraft elsewhere. With the decrease in popularity to North African resorts (obvious reasons) I think they decided to try Malaga again for 2017 however like a previous poster has said, there are now so many airlines that fly there that it probably wasn't viable.
Palma is another example of more or less every U.K. Airport serving it, with an array of different airlines