It hasn’t “evaporated” but has reduced in size and airlines can make more money flying their aeroplanes somewhere else. If the MAN crows could look past narrow conspiracy theories about London always doing the north down for even half a second, you’d see that with United, they have chosen to add service from Newark to Nice, Naples, Faro and Malaga for S24. American has gone to Copenhagen, Nice and Naples (they’ll be busy). JetBlue has gone to Edinburgh and Dublin
Any of that capacity could theoretically have come to MAN. None of it has. The airlines are concluding there is more money to be made elsewhere.