This isn't a pop at Southend-on-Sea Airport but it does appear to be an airport with cost implications that don't affect other easyjet airports serving London.
Diversions due to a Cat 1 ILS, restricted opening hours and a short narrow runway all have impacts to their Southend operation that just don't affect Easyjets other London bases.
Saying all of that, non of those same issues has had any effect on London City Airport's ability to attract business.