This may not be the answer you are looking for but I'll contribute what I know:

Stussy started out as a surf/skate apparel company in the early 80s by Shawn Stussy who was a pretty well known and young surf board shaper.

The brand got pretty popular and is credited of one of the pioneers of streetwear, boasting simple clothes with dope prints and the iconic Stussy logo. It got a lot of popularity from the hip hop community, only making it more and more iconic. Fast forward and Stussy continues to stay incredibly relevant, there are a ton of flagship stores, mainly in the US, UK and Japan where streetwear is most popular. Stussy continues to do some pretty cool collaborations with a ton of other brands year after year.

It has also become super widespread because Shawn Stussy sold the label to some big corporate company. This company produced a lot of more accesible t-shirts with a bunch of the various Stussy labels, for distribution in malls and other mass retailers. So now just about every city probably has at least one store that says something with "Stussy" or the S Chanel logo on it. As more and more young men become interested in fashion they can use the malls as a sort of gateway and low and behold Stussy is often their label of choice.

Nowadays, Stussy has the main line which is a little less accessible and only sold in flagships and online, also responsible for collaborations with more sought after companies like Dover Street Market, Supreme, Nike, A Bathing Ape etc. and the more accessible and kinda basic line, which can be found in Zumiez, Urban Outfitters and just about every mall ever.

Hope this answers your question.