I really dont think there needs to be any "story"
All you need is money and time. Stefan obviously has plenty of both.
Third ingredient is enough space to keep all that stuff away from a woman..
I can see some garden and countryside in bg so it looks like a nice cottage house next to a main house full of retro bling haha
Concerning collection itself, Its biiiiggg, but see no magic.
There is so much very interesting bikes, frames you can buy online EVERYDAY..
If you add a built network of personal contacts of people with same interest, it can go quite fast
(having those first two crucial ingredients)
edit:
Of course, you also need a good taste to be able to build some of the beauties Stefan has had