Starting a route from MME to LCY at the beginning of July was less than brilliant. This route was always going to be business targetted - Eastern with puddle jumpers can't possibly have the economy of scale that comes with a 737 - leisure travellers would likely stick with the train against high fares. Corporate offices began emptying out in March and Zoom has taken over from business travel. Even if there had not been a pandemic, a business-centric route always sees low demand in July/August with people on holiday.
The London City route has to generate respectable numbers of business travellers in September and October. If not, it's a waste of subsidy