A huge omission in here is that Chelsea weren’t an option during the formative years of a lot of non-white people as they were perceived as a racist club by association and the antithesis of anything a non-white person should be supporting. That, coupled with the open arms and feeling of union Arsenal offered, makes for a no-brainer for an entire generation of support. In fact, if you’re of a certain age, you have to divorce what Chelsea were from what Chelsea are to get your head around the shift that would be deemed incredulous a couple of decades ago. On top of that, Tottenham were proudly and staunchly “Yid Army” which is isolating in itself and again made Arse an effortless choice to select as a non-white person choosing a London club. So this allied to the players and style of football they had, gave a huge, unchallenged advantage for literal decades.
The footballing landscape has changed beyond recognition in London from the 80’s until now and opened the doors for change on an epic scale. A scale that’s incomprehensible for those that don’t know what these clubs used to be perceived as.
Yes. In Inner South London, with its huge and growing black population, 'traditional' support was divided between Chelsea and Millwall. While some black supporters followed this trend (Ian Wright was a Millwall fan back in the day),, for most of the 80s and early 90s, the foul reputation of both teams was enough to put any black person off, and neither had the attraction of success either - which made things worse, as both fanbases were dominated by an unloved hard core.
Arsenal always had historic pockets of South London support from the Woolwich days, and was clearly the most successful of the London teams. Spurs had their black fans, but were more clearly tied to their traditional areas of support, and were less clearly successful over the period.
(Crystal Palace also did well out of the trend; their support base has grown out of Croydon, and has shifted closer to the Thames, and down towards Brighton. If they can push through to a Top 10 place consistently, they have a massive potential fanbase to unlock.)
One thing about Chelsea: even before the Roman era, they always seem to have the biggest fairweather fanbase. Their proximity to fashionable London might have something to do with it. When they are flying high, they do well, but a lot of those fans might drop off if they look as though they will go through a prolonged trophy drought.