Back in the days when I was young LTN, well airliner wise it was a holiday IT airport, Britannia, Monarch, I recall Laker 1-11's doing some ski flights and military charters, LTN had some freighters and not much besides, look at it today!
STN, in the mid 80's pretty much all STN had were some three based Air UK sheds and one Dan-Air jet for summer IT seasons, it had freighters and kind of ressembled what the other side of SEN looked like last time I was there ... A knackers yard
When they totally redeveloped STN, new terminal, underground railway line etc. etc. etc. people were laughing it and referring to it as a white elephant and if it wasn't for the introduction of LCC's it might still be a white elephant perhaps!
So, yes, Stobart have taken a big financial risk with SEN, a risk that nobody else was prepared to take on, and good luck to them.