You're speaking as though this is something new. It isn't new. What is new is that M as a whole is now occupying a price bracket clearly above what it used to and across every tier.
IMHO in terms of the following and enthusiast space, it has always been this big if not bigger. Certainly 10 years ago. Making them faster has also been happening since time immemorial. 20 years back it was Old Dutch Racing in KZN, Sav & RGM up here and various others around the country playing with NOS, superchargers and turbos. Chiplogic doing things the old fashioned way and soldering/desoldering actual chips... trying to get the unichip not to lose the adjustments on it... rats nests of wires etc. Tuner wars were not only happening 5 or 10 or 15 years ago. Even in my Dad's days there were 'informal' tuner wars.
It is just that there is more media around what is happening now as opposed to reading a heavily dumbed down article in a magazine or overly technical forum post somewhere. Bear in mind that BMW's total M production numbers are tiny relative to the car buying population. You are also receiving and consuming a lot of curated media fed to you because of your interests and of events with a high concentration of these relatively (in the grand scheme of all cars) rare things. That is the disaster of social media with all aspects of life - it makes extraordinary things seem ordinary and commonplace. Then as a result, everyone feels either it is bigger than it really is or they are worse off than they really are

. We in SA are one of the largest markets for M cars globally and we already don't see a huge amount in 'daily life'... until the time comes to meet for an event or club thing.
There have been BMW club sport series, race series, various events and even official recognition of clubs for decades. Love of BMW and M is not something new. There is no 'huge following gained'. It is formalising and publicising what already existed IMHO. New people are entering and because it is new for them, it must be new for everyone. BMWs have always been the best at this kind of thing (occasionally challenged by others) but there is a reason the M3 has been the benchmark since I was old enough to read until now.
That isn't to say (as most who have made the switch have found) that the 911 is not the thing M3/4 owners think they have (regardless of what articles or spec sheets say) but that is another matter entirely. You must also understand though, that as much as this segment is a big segment, if you don't have those constraints (and this is a much smaller market), the value prop largely collapses. There is a big segment of those people and as they age-through life become targets for supercars or 911s or Caymans (Even Z4s). BMW unfortunately has no credible answer to this that makes sense (the M8 is not it). An i8 with a B58/S58 in it would have cleaned house even in the higher tiers. Alas we can dream.
I think where
@TBP88 's comments stem from is the fact that these are not cheap cars anymore (not by any metric) and the point is that (I guess in our old minds) if you can spend R1.5M on a car you probably have a R4.5M+ house at least and are earning a decent amount of money hence are unlikely to have the constraints that would make a G87 the car to pick. This was not the case with cars, say, pre 2015 where it was an 'average guy' that would be able to realistically buy an entry level M or used higher tier one. A reasonably new Porsche (obviously not the same model year, but still with driveplan) likewise would have been out of the question for someone shopping around there, whereas today when you're talking R1.5M it absolutely isn't.
On another note, please don't open more accessory or tuning shops in SA. There are more than enough already

where are you looking that there are not a lot of options let alone at the dealer themselves selling M Performance things?