I don't understand the recent Rolex SS craze/shortage. What am I missing?

In a video that Producer Michael made a few weeks ago about selling part of his collection, the shop he went to was proclaiming "the market is very difficult, not so much demand for this model, so we can only offer you XX". One comment on the video was that it's always a difficult market when you sell, but when you buy all the watches are rare and in high demand.