As with Perpignan the location is a a significant attraction, though engaging the local(ish) community would gain a greater benefit. The other thing to take into account is there are plenty of ex-pat "noisy northerners" in and around London but most do not not turn up unless their team are playing London Broncos, why they do not turn up for other matches is for them to answer. There had been talk of needing to attract the NZ/Aus ex-pat/traveller community that also drew little benefit. There was a lot of hope when Junior RL in London grew at its fastest rate with free tickets available to parents of junior players. They even had periods of giving away tickets in one of the main London newspapers. You can debate how successful or not those tactics have been but there is no convincing case for them.
Good engagement with the existing fanbase and local communities has been suboptimal, you could also argue the same for the matchday experience. Though crucially the club moving around so many times is one of the other big factors, though when they initially move they get a boost but have often not managed to build on it.