SEN was failing to attract new operators before the Brexit referendum and that has not changed since. Over the same period other London airports seem barely able to cope at times with the demand. On the face of it Southend Airport has grown significantly over the last few months but the growth has been organic.
As for the reports of operators meeting with Stobart and having the grand tour of the airport - perhaps carrying out technical assessments - I don't doubt it for a minute. But when it all goes back to head office other options are preferred.
One day the groundwork being carried out may produce results. Who knows what will be the trigger? Perhaps a falling out between an operator and another airport.